下列属于雌雄同体的动物是（）
A.中华绒螯蟹
B.日本沼虾
C.藤壶
D.龙虾
参考答案：C
Land animals are believed ______ from sea animals.
A．to have developed
B．to have been developed
C．having developed
D．having been developed
几种常见金刚石钻头底唇面形状的特点是什么？
