Question

They _ in the library at present. ( work)

Answer 1

HEY FRIEND,

HERE IS YOUR REQUIRED ANSWER,

They are working in the library at present.

--present continuous tense is used in it.
--present continuous tense is used because it is mentioned in the question that the work is being taking place at present.

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Answer 2

They are working in the library at present.

• The given sentence is in the present continuous tense. The verb used should also be of the same tense.
• This tense is formed by subject + present participle (-ing) of the main verb with the present continuous verb to be, for example, "am, is, are".
• These tenses give information about the event which is still happening now.
• These tenses are composed of two parts.