差压变送器中测量膜盒内充硅油的目的是（）
A.防止膜片和变送器震荡
B.增强膜片的弹性和强度
C.使放大器的放大倍数稳定
D.防止双向过载
参考答案：A
Today the forests are getting fewer and fewer. We must _______ down too many trees.
A．keep people from cutting
B．prevent people from cutting
C．stop people cutting
D．all the above
自动低频率减负荷装置可以根据需要安装在电力用户内部；且用户应积极配合，不得拒绝。
