Assertion: Half-life of a certain radioactive element is `100` days. After `200` days, fraction left undecayed will be `25%`.
Reason: `C_(t)/C_(0) = ((1)/(2))^(n)`, where symbols have standard meaning.

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 the reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If assertion is false but reason is true.

Answer

A

Explanation

Number of half-lives `= n = (t)/(T) = (200)/(100) = 2`
`(N)/(N_(0)) = ((1)/(2))^(n)`
`((1)/(2))^(2) = (1)/(4) = (1)/(4) xx 100%`