绦虫和蛔虫均为肠道寄生虫，蝗虫对禾本科作物危害很大．青蛙被称为“田园卫士”．绦虫、蛔虫、蝗虫、青蛙它们分别属于（　　）

如图，小明将自己用的一副三角板摆成如图形状，如果∠AOB=155°，那么∠COD等于（　　）

    There are four seasons in a year in Canada. They are spring, summer, autumn and winter. In spring, the weather is warm and sunny. I like to fly kites. In summer, it's hot. I like to swim. I often wear a pair of glasses and a hat. In autumn, it's always cool. I like to go to the park and ride down the street with my friends. In winter, it's cold and snowy. I like to go outside to skate and ski with my friends. Sometimes we make a big snowman, and then we dance and sing around it.

萝卜的根形是由位于两对同源染色体上的两对等位基因决定的。现用两个纯合的圆形块根萝卜作亲本进行杂交，F₁全为扁形块根。F₁自交后代F₂中扁形块根、圆形块根、长形块根的比例为9:6:1，则F₂的圆形块根中杂合子所占的比例为（）