[单选题]布氏姜片吸虫的致病虫期是
A.虫卵
B.尾蚴
C.囊蚴
D.成虫

此题要求改正所给短文中的错。对标有号的每一行作出判断；如无错误，在该行右边横线上面一个勾(√)；如有错误(每行最多只有一个错误)， 则按下列情况改正：
多一词：把多作的词用斜线(/)划掉，在该行右边横线上写出该词，并也用斜线划掉。
缺一词：在缺词处加一个字符号(∧)，在该行右边横线上写出该加的词。
错一词：在错的词下划一横线，在该行右边横线上写出改正后的词。
注意：原行没有错的不要改。
Many experts worry about the effects of television in young 76. ______
people. According to studies, any children spend more time 77.______
watching television than they spend in school. Because so much 78.______
viewing, children may not develop the habit of reading and 79.______
the ability enjoy themselves. No one worries much about the 80.______
radio programs young people listen, although radios can be very 81.______
noise. Experts also wonder about the effects of television 82.______
commercials. On one year the average child will see 25,000 83.______
television commercials, all planned and written for grown-ups to 84.______
make child