Critical Reasoning

Potato cyst nematodes are a pest of potato crops. The
nematodes can lie dormant for several years in their
cysts, which are protective capsules, and do not
emerge except in the presence of chemicals emitted
by potato roots. A company that has identified the
relevant chemicals in planning to market them to
potato farmers to spread on their fields when no
potatoes are planted; any nematodes that emerge
will soon starve to death.

Which of the following, if true, best supports the
claim that the company’s plan will be successful?
(A) Nematodes that have emerged from their cysts
can be killed by ordinary pesticides.
(B) The only part of a potato plant that a nematode
eats is the roots.
(C) Some bacteria commonly present in the roots of
potatoes digest the chemicals that cause the
nematodes to emerge from their cysts.
(D) Trials have shown that spreading even minute
quantities of the chemicals on potato fields
caused nine-tenths of the nematodes present to
emerge from their cysts.
(E) the chemicals that cause the nematodes to
emerge from their cysts are not emitted all the
time the potato plant is growing.

OA is D

Please explain.