下列生物与生物之间的关系，属于竞争关系的是[ ]
A．狐狸与野兔
B．工蜂与蜂王
C．水稻与稗草
D．跳蚤与小狗
答案：C
Many trees ________ along the streets every year. So the air is very fresh now.
A．plant
B．are planted
C．planted
D．were planted
中国工程咨询协会的理事实行任期制，每届任期( )年。
A．4
B．3
C．2
D．1
