Which of the following poses the biggest problem when applying the Biological Species Concept (BSC)? A)A unicellular parasite that exchanges gametes with a partner inside the host body

Which of the following poses the biggest problem when applying the Biological Species Concept (BSC)?
A)A unicellular parasite that exchanges gametes with a partner inside the host body but the process has never been observed and genetically confirmed.
B)An African tse tse fly and a Canadian black fly are crossed in a laboratory and produce viable progeny.
C)A population of ectoparasite which is genetically distinct from another population and is separated from the other population by a mountain range. The two populations do not interbreed with one another.
D)Two similar looking adult endoparasites which do not interbreed with each other and occupy distinct microhabitats within the host.
E)Two similar populations of ectoparasitic arthropods having incompatible genitalia, which prevent mating.
Which of the following statements is true?
A)Well-nourished hosts are more susceptible to infection than malnourished hosts.

B)The increase in Schistosoma transmission after dam construction was a result of an increase in suitable habitat for the mosquito vector.
C)Viral co-infections which compromise the host immune system can increase host susceptibility to opportunistic parasite infections.
D)Person-to-person transmission is the hallmark of reverse zoonosis.

E)Adequate sanitation methods enhance the transmission of parasites such as Entamoeba histolytica and Cryptosporidium.