+1 for
C.
A.
The number of them carrying the Ebola virus will increase as more and more people consume tainted bushmeat, the meat of African wild animals, and come into contact with infected apes.
B. The number of humans carrying the Ebola virus will increase as more and more people
had consumed tainted bushmeat, the meat of African wild animals,
and have come into contact with infected apes.
C.
The number of humans carrying the Ebola virus will increase as more and more people
consume tainted bushmeat, the meat of African wild animals,
and come into contact with infected apes. -->
Correct use of Verb-Tense form D. As a number of people consume tainted bushmeat, the meat of African wild animals, and come into contact with infected apes,
the number of them carrying the Ebola virus will increase.
E. As more and more people
consume tainted bushmeat, the meat of African wild animals,
and are coming into contact with infected apes, the number of humans carrying the Ebola virus will increase.
Hence,
C.