Recently, a reader asked about the difference between the present perfect tense and the past simple tense in tag questions. Tag questions are short questions seeking confirmation or expressing doubt at the end of a sentence. In "You knew the answer to the question, didn't you?", "didn't you?" is a tag question seeking confirmation that you knew the answer. "You have bought new furniture, haven't you?" is in the present perfect tense. "You bought new furniture, didn't you?" is in the past simple tense. We use the present perfect for things that happened at an undefined time in the past, things that happened repeatedly in the past, things that happened in the past but in some way affect the present, in questions with "ever" and in statements with "never." Have a look here https://learningenglish.voanews.com/a/everyday-grammar-simple-past-and-present-perfect/2752310.html and watch the video and read the article below the video for some great information. If I visit your house for the first time in a long while, and I see that you have different furniture than I remember, I might say "You have bought new furniture, haven't you?"
We use the past simple for things that happened at a specific time in the past. If I see your car in the furniture store parking lot one day and see you or call you on the phone later, I might say "You bought new furniture today, didn't you?"
We do not mix the tense of the verb in the statement and the tag question. We would not mix "You bought new furniture,..." with "...haven't you?". The verbs in the statement and the tag question must be in the same tense.
Thanks again for the question!
Related to the question of whether we must use or must avoid the use of "to" before the infinitive, is the question of the particle "to" implies the infinitive so that in idiomatic English the infinitive is not repeated. What?????? OK, if you have not yet read the question and answer about using "to" before the infinitive , please read it before continuing. Cool. Now that you have read when we must use and may not use "to" before the infinitive, I will explain when the "to" allows you not to state the infinitive at all. An example: "Mom, may I go to the movies with you and Dad?" asked Sarah. "No, you may not," replied Sarah's mother sternly." "But why not?" asked Sarah pleadingly. "Pleaaaaase, Mom?" "Because you're not allowed to ," responded Sarah's mother. Sarah's mother does not answer, "Because you're not allowed to go to the movies" because the particle "to" implies that she is not allowed to do what she asked permission to do, namely, go with her parents to the movies. Another example: "Why didn't you dance with John at the party?" "Well, he never asked me to ." Again, there is no need to repeat the infinitive "dance" in the answer because "dance" is implied by the particle "to." A third example: "Why didn't you bring home pizza? I told you I wanted pizza!" "Oh, I'm sorry. I forgot to . " Also in this dialog, the particle "to" implies the infinitive "bring" in the response. Do we ever include the infinitive after the "to" in the answer? Yes, we sometimes include the infinitive for emphasis. For example: "I want to eat pizza tonight." "Yuck, I don't want to eat pizza. You know I hate pizza. Let's get Chinese food instead." In summary, we don't have to and usually don't repeat in the response to a question or previous statement the infinitive contained in the question or statement. We say that in the response the infinitive is implied by the particle "to." Sometimes, though, we repeat the infinitive for emphasis or to make a point -- like the "you know I hate pizza" in the example dialog.
Thank you for the question. Most students are taught that the infinitive consists of "to" plus the verb. While we often must use "to" with the infinitive, "to" is not actually part of the infinitive and it is sometimes incorrect to use "to" before the infinitive.
With most verbs sentences follow the format:
Subject + verb + to + infinitive.
I want to eat pizza.
Johnny likes to swim .
He decided to go to the beach.
The ¨to" in these sentences is REQUIRED :
"I want eat pizza" is INCORRECT .
"Johnny likes swim" is INCORRECT .
"He decided go to the beach" is INCORRECT .
However, many verbs are not followed by "to" before the infinitive. Sentences with these verbs follow the format:
Subject + verb + infinitive.
I heard the band play beautiful music.
Ed's boss lets him go home early.
Pete's mother makes him wash the dishes.
The use of "to" is not permitted. No, no, no, no, no:
"I heard the band to play beautiful music¨is INCORRECT .
"Ed's boss lets him to go home early" is INCORRECT .
"Pete's mother makes him to wash the dishes" is INCORRECT .
In addition, there is an entire category of verbs called modal verbs or helping verbs with which the marker "to" is also FORBIDDEN :
Can: I can dance .
Could: I could run fast when I was young.
May: I may go to Santa Marta on vacation.
Might: It might rain tomorrow.
Must: You must obey the laws of the countries you visit.
Shall: Shall we leave now?
Should: You should drink more water. Will: I will help you with your paper. Would: I would eat supper earlier if I didn't work so late.
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