请问这道英语语法题There ought to be less anxiety over the perceived risk of getting cancer than ＿in the public today.A.exists B.exist C.existing D.existed 为什么选A项?

than 在此为比较状语连词， than exists in the public today中，than后省略了there，且exists 的主语anxiety也被省略。属于承前省略。
还原则为There ought to be less anxiety over the perceived risk of getting cancer than （there） exists in the public today.
句意为：对潜在的患癌症的风险的担忧程度不应该超过公众中已经存在的（担忧）。

这是个比较句，比较句前后的结构要一致
There ought to be less anxiety over the perceived risk of getting cancer than (there) exists（anxiety ) in the public today.
there be 和there exist 都表示存在
去掉相同的成分就变成这样的
一开始我觉得后面的是anxiety 的修饰语，应该用existing ,放在从句里，作exist 的主语，又不能省略连接词，想了想，觉得还是这样解释吧！

我咋 感觉应该选c呢！

这个句子可以这么看there ought to be less anxiety than (the anxiety that) exists in the public today. 因为前后比较的主体相同，所以后边省略了the anxiety
(over the perceived risk of getting cancer 修饰anxiety)

应该选C吧，肯定不是A。

因为这句话本来应该是Less anxiety ought to be over the perceived risk of getting cancer than exists in the public today. 所以这句话的主语是anxiety是一个单数 这句话的两个动词时ought to be和exists 所以两个动词都应该是第三人称单数
over the perceived risk of getting cancer只是一个修饰 你也可以放在前面 变成 over the perceived risk of getting cancer, less anxiety ought to be than exists in the public today.

主要从意思上区分.在当今社会,对于检察到患癌症的危险,比起实际存在的,本不应该有那么多的焦虑.就是说,把句子分一下,就好做了.弄清比较对像,因为than两边,结构对等.over the perceived risk of getting cancer ,对于...

应该是省略了主语