Nhận biết (M1)

Physical barriers, chemical defenses, and protein defenses are the three main categories of plant defense mechanisms. The poplar tree uses a __________ the trees produce chemicals that prevent certain herbivorous insects from feeding on the trees’ leaves.

Which choice completes the text so that it conforms to the conventions of Standard English?

• A.

  chemical defense:

• B.

  chemical defense,

• C.

  chemical defense

• D.

  chemical defense and