Option (b)

As a student may answer a question or he may not, So let’s verify the total chances that he can take with a question, i.e. He can take 6 chances with a question namely A,B,C,D,E or not answering it. So with every question he can take 6 chances. So total number of chances is $6^{150}$.

From this, we have to deduct these chances: - Total number of ways of answering zero questions as well as one question exactly, which is $1+(150\times 5)=751$. So answer is $6^{150}-751$.