Read the technical passage to answer Numbers 5 through 7.

Which of these is the main argument for not closing the waterways when fish with lesions are observed?
	A	Some toxins from Pfiesteria are harmless to humans.

	B	Only one type of fish can be infected with Pfiesteria.

	C	The toxins from Pfiesteria will break down in one hour or less.

	D	It is uncertain whether all fish with lesions are infected with Pfiesteria.