【小题2】Which of the following might explain the origin of viruses?
A.They evolved from the fossils of large organisms.
B.They evolved from parasites into independent organisms.
C.They evolved from the T-cells in animals.
D.They evolved along with their host cells.
【小题3】The underlined word “plausible” in the last paragraph probably means ________.
A.reasonable
B.common
C.creative
D.unbelievable
【小题4】What can we conclude from the text?
A.Viruses live longer in human host cells than in animals’.
B.Viruses will become more like bacteria as they evolve.
C.It may take a long time to understand the origin of viruses.
D.The author is optimistic about future virus research.
