The _____(careful) they drive,the safer they will be.
问题描述：
The _____(careful) they drive,the safer they will be.
答
The more carefully they drive,the safer they will be.(他们驾驶越细心,就会越安全.）
the +比较级,the +比较级 表示“越……就越……,由于这个空格修饰的是动词drive,所以应用careful的副词形式carefully.