单项选择题
Questions 18 to 21 are based on the following talk about a singer.
A.War victims B.Flood victims C.People who are starving D.People who have got AIDS
A.trace B.way C.time D.period
A.Genes may contribute to some common diseases B.Environmental factors cause more diseases than genes C.It is common that most fatal diseases are caused by genes D.It is impossible to get clear-cut genetic answers at present