The major product in the following reaction is:

Which of the following enzymes requires copper for its activity?

If $y = \log_{\cos x} \sin x$,then $\frac{dy}{dx}$ is equal to

The number of acidic hydrogen atoms in $but-1-yne$ is ........

Coal tar is the main source of

$A$ student has to answer $10$ out of $13$ questions in an examination,choosing at least $5$ questions from the first $6$ questions. The number of choices available to the student is: