若点P（a，b）在第四象限，则点M（-a，a-b）在第______象限．
∵a＞0，b＜0，
∴-a＜0，a-b＞0，
∴点P在第二象限．故填：二．
The report indicated that 45% of students were in jobs not_______specific qualifications.
A．requiring
B．to be required
C．being required
D．to have required
在自然光线下，正常人瞳孔直径约为 ( )。
A．0.5～1mmB．1.5～2mmC．2.5～4mmD．4.5～6mmE．6.5～7mm
