Assertion (a): The conductivity of a semiconductor increases with rise of temperature.
Reason (r): On rising temperature, covalent bonds of semiconductor break.
1: Both assertion (a) and reason (r) are true, and reason (r) is the correct explanation of assertion (a).
2: Both assertion (a) and reason (r) are true, but reason (r) is not the correct explanation of assertion (a).
3: Assertion (a) is true, but reason (r) is false.
4: Assertion (a) is false, but reason (r) is true.