As is known,____ (play) team sport is popular all over the world, and participation in sporting____ (activity), such as football or basketball, is ____(benefit) to us in many aspects.

    To begin____, it can build up our bodies and help us keep fit physically,____in turn enables us____(avoid) overweight and other problems, such as high blood pressure.____ (add), it is a good way to develop some useful team skills, teamwork and strategies ____(include). Last but not ____(little), we often play sport for social reasons, for it is a good way of making new friends.

    ____, everyone should take an active part in team sports.

下列有关哺乳动物精子和卵细胞的发生以及受精作用的叙述，正确的是(　　)。