Some important Rule about Model:-

Rule 1,:- A model only could be a Auxiliary or Helping verb .

For example:- (1) He will come.

(2) He could come.

(3) He may come.

Here :- will, could, and may act like a model

Rule 2:- A model act like a Auxiliary verb or Helping verb so it always take a helping verb :-

For example:-(1) He will come.

Here:- come is main verb.

Rule 3:- After a model we can't use any adjective or infinitive.

For example:- (1) He will true to his words (x)

(✓) He will be true to his words.

Reason:- we know that after a model we always use a main verb but we can't use any adjective .

Here:- True is adjective we can't use it after a model so , that's why we take a verb(be) After a model

Infinitive example:- He must to do the work (x)

(✓) He must to do the work

Reason:- After a model we can't use any infinitive

Here:- (To do) a infinitive.

Rule 4:-. after a model we always take a verb ( v1)

Will/Shall:-

:- past form of will is would .

:-past form of shall is should or would .

Here we use should for advice. For example:- He said that we should help the poor.

In this case:- we just giving advice.

(2) He said that we would help the poor.

Here:- Would show willingness.

{÷}Rule 5:- If we want to make a model in the past ,we use (Have) after the model.

{÷} Rule6:- If we want to make a model in future sense we use (be) After a model.

Example:- He must do the work.( उसे काम करना चहिए।

(2) He must have done the work ( उसे अवश्य ही काम करना चहिए था।

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******** Will/ shall itself use in a future form so we can't use this in past form to use ( have).