Question

Choose the option that best fills in the blank to complete the sentence logically and correctly:

The instructor added the restriction that all projects had to be ______: no student could research an area that had been investigated previously by anyone else.

• A. Acceptable
• B. Useful
• C. Extensive
• D. Original

Answer 1

The correct option is D Original

Option A: 'Acceptable' means 'moderately good or satisfactory'.
Option B: 'Useful' means 'something that is of good use or function'.
Option C: 'Extensive' means 'large in amount or scale'.
Option D: 'Original' means 'created personally by someone'.
From these words, 'original' is the most suitable one because it completes the sentence in meaning: the instructor had added the restriction that the projects should be created by the students personally, and no student could research on something that had already been touched upon by someone else (making it unoriginal).
Hence option D is correct.
The other words, 'acceptable', 'useful' and 'extensive' do not complete the sentence in meaning.
Hence options A, B and C are incorrect.