写出同时满足下列两个条件的数a：a2=16，-a＞0；a=______．
∵-a＞0，
∴a＜0，
∵a2=16，
∴a=-4．
故答案为：-4．
I visited Hangzhou several times, ______ is famous for the West Lake.
A which B where C it D what
混作
