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There is a confusing sentence:

"The experts from the London Zoo thought that this puma must have been in the possession of a private collector and somehow managed to escape."

Should we use "must has been" in this sentence, since "puma" is NOT a plural?

Thanks for your comments.
Comments  
No, much the same way you wouldn't use the first person singular below:
She must have her gloves.
She will have her gloves.

But you must use 'has' in these cases:
The puma has been in the possession of a private collector.
She has gloves.


Hi Warrener, Your question......

>>Should we use "must has been" in this sentence, since "puma" is NOT a plural?

I am afraid not. Verbs used after modal ( and auxiliary)words must remain in their basic form. (Must, shall, will, can ought to, etc…)

Ex: 1) She must complete her assignment tonight before the presentation tomorrow morning

2) May I have this paper ?

3) I have to get up early tomorrow

4) She should listen to her parent’s advice.

Goodman

Me love English
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After can, could, will, would, shall, should, may, might, and must, the only form of have which is possible is have itself, never has or had. (The word not and/or other adverbs may intervene, as in could not have. Even in these cases, only have is possible.)

CJ
WarrenerThere is a confusing sentence:

"The experts from the London Zoo thought that this puma must have been in the possession of a private collector and somehow managed to escape."

Should we use "must has been" in this sentence, since "puma" is NOT a plural?

Thanks for your comments.

In addition to others' comments, 'has' can follow 'must' only when the word 'must' is used as a noun.

(E-x) The word 'must' has been used several times in your essay.
you cant say must has been, cause modals like must, can , could , might .....etc take base form of verb after it so the base form of has and had is have (must have)
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Bare Infinitive unmarked form of the verb (no indication of tense, mood, person, or aspect) without the particle "to"; typically used after modal auxiliary verbs; see also infinitive eg: "He should come", "I can swim"