顺利、有效地完成某种活动所必须具备的心理条件称（）。
A、动机
B、内驱力
C、能力
D、气质
参考答案：C
We were prevented ________ the project on time by the bad weather. [ ]
A. to complete
B. completed
C. completing
D. from completing
下列含有非极性键的化合物是：
A．MgCl2
B．Na2O2
C．H2O
D．N2
