题目

---How far is the library from our school?         --- It’s quite near. Just go______ the street. A. cross      B. across    C. near  D. to 答案：B受精完成的标志是 A．雌、雄原核形成                  B．精卵相遇，发生顶体反应 C．精子接触透明带                  D．卵黄膜和透明带间出现两个极体