Select the most appropriate option to fill in the blank.

Constructive thinking should be developed through _________ reading.

extensive

The most appropriate option to fill in the blank is extensive.

The sentence is about the importance of extensive reading for developing constructive thinking. The word "extensive" means covering a wide range or area. It is the most appropriate word to use in this context, as it conveys the meaning of reading a wide variety of materials to gain a broad understanding of different perspectives.

The other options are not as appropriate.

• Avid means having or showing a great interest in something. This is not the right word to use, as it does not convey the same meaning as "extensive."
• Narrow means limited in scope or range. This is not the right word to use, as it does not convey the meaning of reading a wide variety of materials.
• Brief means lasting for a short time. This is not the right word to use, as it does not convey the meaning of reading a wide variety of materials.