单选题We may infer from the fourth paragraph that ______.A humans have been growing food crops more than ten thousand years.B humans have learned how to produce biofuels for a long time.C humans are just on the beginning of making biofuels.D a cell wall incl
题目
单选题
We may infer from the fourth paragraph that ______.
A
humans have been growing food crops more than ten thousand years.
B
humans have learned how to produce biofuels for a long time.
C
humans are just on the beginning of making biofuels.
D
a cell wall includes four hemicellulose.