If you turn your bag_,the books will fall out.A.back to front B.up and down
问题描述：
If you turn your bag_,the books will fall out.A.back to front B.up and down
If you turn your bag_,the books will fall out.A．back to front B．up and down C．upside down D．back and forth
答
选C
【upside down】是【颠倒,倒置】的意思
翻译：如果你把你的书包倒置,你的书就会掉出来.