The danger of crops becoming extinct before scientists can study them is A.
future scientists will not have jobs.
B.
only scientists fully understand how useful plants can be.
C.
opportunities for improved crops or new medicines will be lost.
D.
scientists have not yet developed effective classification standards for plants.

c

Explanation:

it makes the most sense

but there is no

i guess you forgot putting it.

you didn't give any options but heres what i can tell you: an inference is likely to change based on additional observations. the latter is something that you have seen or sensed using your sensory organs while the former is like a conclusion out from what you have observed.