目前一般把PH值小于（）的降水都称为酸雨。
A、4.0
B、5.6
C、6.5
D、7.0
参考答案：B
There are _______ visitors to the wetland park, and the number is becoming _______ now.
A．thousand of; larger and larger
B．thousands of; more and more
C．thousands of; larger and larger
D．thousand of; more and more
抗拉强度
