A:to buy, to sell
B:to buy, selling
C:buying, selling
D:buying, to sell
____
(从左到右填写)
如图甲所示,验电器A带负电,B不带电.用带有绝缘手柄的金属棒把验电器A、B两金属球连接起来的瞬间(如图乙所示),金属棒中( )
计算:32﹣20150+tan45°.