Ageratum ( ), (whiteweed in the USA), is a genus of 40 to 60 tropical and warm temperate flowering annuals and perennials from the family Asteraceae, tribe Eupatorieae. Most species are native to Central America and Mexico but four are native to the United States.
Can we infer the following?
Scientists are unsure or not in firm agreement as to the exact number of species in the genus Ageratum.

pick from the following.
 A). Yes.
 B). It's impossible to say.
 C). No.
The answer is:
B).