向家坝水电站工程枢纽由拦河大坝、泄洪排沙建筑物、厂房等组成。其拦河大坝采用()重力坝。
A.常态混凝土
B.碾压混凝土
C.预应力混凝土
D.素混凝土
参考答案:A
A recent survey shows that the number of children who from the countryside with their parents ________nearly 320,000 in Beijing.
A.comes; are
B.come; is
C.come; are
D.comes; is
用物理的方法杀灭一切细菌称为________。