Answer:
It looks like the sentence is correct; all you need is capitalization.
"Do you think a rainbow is beautiful?" is correct.
In my opinion its C all the other answers are just examples of daily subjects
<u><em>Subject. A subject in grammar is the first part in a sentence about which the second part, the predicate, tells something.</em></u>
It isn't simile, because there is no comparison to anything, and it isn't ironic.
