【单选题】

What does the comment "This is logical." in line 5 of the first paragraph (underlined) mean
A．There is no clear way to determine the extent of our ancestor's knowledge of plants.

B．It is not surprising that early humans had a detailed knowledge of plants.
C．It is reasonable to assume that our ancestors behaved very much like people in preindustrial societies.
D．Human knowledge of plants is well organized and very detailed.