Assertion: In taking into account the fact that any object which floats must have an average density less than that of water, during World War I, a number of cargo vessels were made of concrete.
Reason: Concrete cargo vessels were filled with air.

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If the assertion and reason both are false.

Answer

A

Explanation

The density of concrete of course, is more than that of water and a block of concrete will sink like a stone, if dropped into water. Concrete cargo was filled with air and as such, average density of cargo vessels = `("Mass of concrete + Mass of air")/("Volume of concrete + Volume of air")`
It follows that the average density of cargo vessels must be less than that of water. As a result, the concrete cargo vessels did not sink.