makes some people appear astonishingly youthful while others seem much older than their actual age?
A. What it is
B. What is it that
C. What it is that
D. Why it is what
网友回答
A. What it is
B. What is it that
C. What it is that
D. Why it is what
解析： 考查强调结构的特殊疑问句。句意为：究竟为什么有些人会看起来年轻得让人吃惊，而另一些人却看起来比实际年龄苍老得多？题干缺少主语，因此如果句首只填一个词时应填what,变为强调结构的特殊疑问句则是What is it that...。