Over time, coral buried by sediments can turn into
a. granite.
b. limestone.
c. coal.
d. atolls.

The right option is; b. limestone.  

Over time, coral buried by sediments can turn into limestone

Limestone is a sedimentary rock that is mainly made up of fossils of calcium carbonate-containing organisms such as coral, forams and molluscs. When corals fragment and die, after some time, sand (sediment) pile up between the corals and the other molluscs which makes the organisms to decay gradually to form calcium carbonate structure which can turn into limestone.

b. 20: 5

explanation:

20% of the worlds population lives in southwest asia, and less than 5% of the world's

land area.