Have you heard about AIDS,   19.    is one of the world’s worst health problems? When AIDS was first reported in the USA in 1981, very   20.   was known about it. There was not even a name for it. No one knew how people got it or how they could fight. People just kept dying of it. The world was   21.     scared of AIDS   21.     wrong ideas about AIDS were passed around. Some believed they would catch AIDS by being around people with it. Some even believed AIDS would bring the end of the world.However,     22.   they were worried about did not happen. In 1995, David Ho, a Taiwanese American, found a way to fight AIDS. Since then, the number of people__23._ has dropped greatly because there are stronger medicines to help them live longer. Today, there is still no easy answer to AIDS, but at least we know more about it. Now it is with experience, not with fear, that we can fight it.
 *AIDS愛滋病 *fear恐懼
【題組】19.
(A)what
(B)that
(C)which
(D)who