题目

Is sport always fun ? One afternoon in the last week of term, I saw three children form my son’s school in tears being comforted by teachers. That morning, my 11-year -old had stomach pains and (21) ______(throw ) up several times when I noticed his sickness. Talking to other mothers, I heard about other children with stomachache or difficulty sleeping the night before. What caused so much suffering ? Sports day ---- not sports day at a highly competitive independent school, but at a large village primary. (22) ______ it causes no problem to the children who can fly (23) _____ the win免疫系统能成功地抵御大多数病菌，却不能抵御艾滋病病毒（HIV），主要原因是 A．没有特效药清除HIV病毒 B．HIV直接杀死在免疫系统中起重要作用的T细胞 C．HIV直接杀死在免疫系统中起重要作用的B细胞 D．机体免疫功能对HIV病毒先天性免疫缺乏所致