Which of the following statements about coral polyps are correct?
\[
\begin{aligned}
A.&\ \text{Corals are found mainly in the tropical oceans and seas.}
B.&\ \text{Corals do not live in deeper waters, i.e. not more than 200--250 feet below sea level.}
C.&\ \text{There should be clean sediment-free water for their growth.}
D.&\ \text{Corals survive through coral bleaching in extreme hot conditions.}
\end{aligned}
\]
Choose the correct answer from the options given below: