Assertion : \[_{Z}{{X}^{A}}\] undergoes \[2\alpha -\]decays. \[2\beta -\] decays and \[2\gamma -\]decays and the daughter product is \[_{Z-2}{{Y}^{A-8}}\]. Reason : In a-decay the mass number decreases by 4 and atomic number decreases by 2. In b- decay the mass number remains unchanged, but atomic number increases by 1 only. [AIIMS 2001]

• 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.
• E.    If assertion is false but reason is true.