Ebola virus is a virus that is frequently and rapidly lethal inhumans. The envelopes around particles of Ebola virus are studdedwith a viral glycoprotein (GP). Researchers hypothesized that, toenter a human cell, GP molecules must be cleaved by a proteaseenzyme, after which they bind with a protein called NPC1 in thehuman cell membrane. Reptile cells do not normally express the NPC1protein, but the researchers modified some reptile cells to expressNPC1. They then exposed the unmodified and modified cells to Ebolavirus, both in the presence of a protease inhibitor that preventsGP cleavage, and without that inhibitor present. They then measuredthe frequency at which Ebola viruses infected the cells. Thesetreatments are summarized below. I. Unmodified reptile cells,protease inhibitor absent II. Unmodified reptile cells, proteaseinhibitor present III. Modified reptile cells, protease inhibitorabsent IV. Modified reptile cells, protease inhibitor present V.Unmodified human cells, protease inhibitor absent Of the following,which is a correct reason for including group V? :
(A) If the virus cannot enter group V but can enter group III,it shows that GP cleavage is not necessary for infection.
(B) If the virus can enter group V but cannot enter group IV, itshows that NPC1 is necessary for infection.
(C) If the virus can enter group V but cannot enter groups I,II, III, or IV, it shows that both GP cleavage and NPC1 arenecessary for infection.
(D) Group V is a positive control.
