7X-8<4.5是方程.______.
7x-8<4.5,虽然含有未知数,但它是不等式,因此不是方程;
故判断为:×.
A.频率相同的波叠加,一定可以发生稳定的干涉现象
B.横波可以在固体、液体和气体中传播
C.纵波不能用波的图象描述
D.波长和障碍物尺寸相近时,衍射现象明显
— I'm afraid a car is too expensive for me.
— But more and more Chinese can _____ to buy it. [ ]
A. expect
B. afford
C. choose
D. offer