单项选择题

It can be learned from the passage that______.

A．it will be difficult for scientists to develop a vaccine for women
B．HIV infects women in the same way with men
C．most women have contracted a variety of HIV from several men
D．it will be easy to develop a vaccine for men

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单项选择题

According to the passage,______.

A．more and more women are infected by HIV virus
B．women have more chances of being infected by HIV virus
C．the aim of the study in this passage is to understand how the virus works
D．many medical studies didn't answer any questions

单项选择题

It will be even more difficult to develop a vaccine because______.

A．most women are infected by a single variant of the HIV virus
B．the virus can duplicate itself into more genetic variants
C．it is difficult to monitor the activities of the viruses
D．technologies are not advanced now