Institution: জাতীয় কবি কাজী নজরুল ইসলাম বিশ্ববিদ্যালয় (JKKNIU) Exam: ক ইউনিট || জাতীয় কবি কাজী নজরুল ইসলাম বিশ্ববিদ্যালয় || 2013
Topic: Sentence (বাক্য), Subject: English Grammar (ইংরেজি গ্রামার)

Best Answer Explained in Below-:

The sentence "At that time, houses ------ consisted of two or three rooms" requires a word that effectively conveys how often or commonly houses were structured during that particular period. Let's analyze the options:

A) "were" – This verb is in the past tense but does not provide any indication of frequency or typicality, which is necessary for the context of the sentence.

B) "usually" – This adverb indicates that it was common for houses, during that time, to consist of two or three rooms. It suggests a typical pattern without stating that it was true every time, making it the most appropriate choice.

C) "are" – This verb is in the present tense and is inconsistent with the phrase "At that time," which refers to a past period.

D) "did" – This auxiliary verb does not fit grammatically within the sentence structure and does not convey the necessary meaning.

Therefore, "usually" is the correct option as it effectively conveys the frequency with which houses were commonly structured with two or three rooms at that time, providing the required context and meaning.