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