Grammar questions

[imany]

Hi

Please check the following sentences:
1-Do you enjoy hiking?
why do we use ing for hiking?

2-Many people like my plan. Will you agree to it?
Many people like my plan. Will you agree with it?
which is right?

3-If you don't understand, don't hesitate to ask a question
If you don't understand, don't hesitate asking a question
which is right?

4-Tomorrow is Mary's birthday. Let's it congratulate it
Tomorrow is Mary's birthday. Let's it celebrate it
which is right?

[gwendolinest]

1-Do you enjoy hiking?
why do we use ing for hiking?

The word “hiking” is a noun here.

2-Many people like my plan. Will you agree to it?
Many people like my plan. Will you agree with it?
which is right?

To agree to something is to give permission for something to be done; to agree with something is to be in favour of something. So, “will you agree to it?” is a request for permission for the plan to go ahead. OTOH, “will you agree with it?” sounds a bit odd to me. If you are asking the other party whether they agree with the statement “many people like my plan”, you can just say “will you agree?” or “do you agree?”.

3-If you don't understand, don't hesitate to ask a question
If you don't understand, don't hesitate asking a question
which is right?

The first one is right; the second one is wrong.

4-Tomorrow is Mary's birthday. Let's it congratulate it
Tomorrow is Mary's birthday. Let's it celebrate it
which is right?

Neither. The correct answer should be:

Tomorrow is Mary’s birthday. Let’s celebrate it.

or

Tomorrow is Mary’s birthday. Let’s congratulate her.

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