Thinking of solving problems: According to life experience and understanding of area unit size and data size, it is known that it is more appropriate to measure the cover area of mathematics textbooks in "square centimeter"; Make corresponding choices.

The cover area of the math textbook we are using now is about 300 square centimeters. ..

Therefore, choose: B.

,9,(20 10? Gongcheng County) The area of the cover of the mathematics textbook we are using now is about 300 ().

Millimeter 2

Square centimeter

Deutsche mark 2

Digital square meter