A:2
B:﹣1
C:﹣1或 2
D:﹣1或 10
防止铁制品生锈的常用措施有____(写一点即可),也可在铁片表面镀上一层锌,表面会形成一层保护薄膜,其中含有Zn2(OH)2CO3.若该物质通过化合反应生成,试推断,反应物除了Zn、水和氧气外,还应有____.
— Can I walk across the road now, mum?
— No, you ________. You have to wait until the light turns green.
Sam fell _____ his bike.