A:was looking
B:had looked
C:looked
D:is looking
日常生活中,不利于维持大气中“碳﹣氧”平衡的做法是( )
试回答下列问题:
8-3=____
8-____=1
8-5=____
8-____=7
8-7=____
8-____=4
8-1=____
8-____=2
8-6=____
8-____=5