The author's attitude towards the developing of HIV vaccine is______.

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

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