Assertion: - A pure semiconductor has negative temperature coefficient of resistance.
Reason: - In a semiconductor on raising the temperature, more charge carriers are released, conductance increases and resistance decreases.
A.Assertion is true, Reason is true; Reason is a correct explanation for Assertion.
B.Assertion is true, Reason is true; Reason is not a correct explanation for Assertion.
C.Assertion is true, Reason is false.
D.Assertion is false, Reason is true.

Hint: To answer this type of questions, first understand the assertion statement and what the statement is trying to say. Once the assertion statement is understood properly, then verify if the reason mentioned can explain the assertion statement or not, check if the reason has covered all the important points that helps to understand the assertion.

Complete answer:
The resistance of a semiconductor decreases with a rise in temperature because of negative temperature coefficient of resistance. The reason being, on raising the temperature, covalent bond breaks and conduction holes and electrons increases, due to which more charge carriers are released, conductance increases and resistance decreases.
So, both assertion and reason are correct, and reason is the correct explanation of the assertion.

Therefore, the correct answer is Option (A).

Note:
This type of question is widely asked in papers, as it acts as a trick question for students. This question is mainly asked to test the understanding of the student and to understand how much grip the student has on the topic. Sometimes there are more than one reason given to explain an assertion and the student might need to choose the correct reason out of the mentioned reasons that best explains the assertion.