1．计算－4×（－2）的结果是··········································································· （ ）
A．8 B．－8 C．6 D．－2
2．如图，由相同的小正方体搭成的几何体的主视图是······································ （ ）
3．如图，跷跷板AB的支柱OD经过它的中点O，且垂直于地面BC，垂足为D，OD＝50cm，当它的一端B着地时，另一端A离地面的高度AC为··············································································· （ ）
A．25cm B．50cm C．75cm D．100cm
4．下列整数中，与最接近的是·································································· （ ）
A．4 B．5 C．6 D．7
