Why does an iron nail float on mercury while it sinks in water?

A) Due to less chemical interaction of iron with mercury than it is with water

B) Iron is heavier than water and lighter than mercury

C) Iron has greater density then water and lesser than, mercury

D) Mercury is heavier than water

This MCQ is part of the UP PSC Previous Year Questions (PYQs) series, focusing on UPPSC Prelims 1994 (GS Paper I)