In alkaline medium, which elements can produce hydrogen?
(A) Zn, Si
(B) Cu, Ag
(C) Cu, N2
(D) Al, C

In an alkaline medium (a basic solution), only certain metals with a standard reduction potential higher than that of hydrogen can produce hydrogen gas by undergoing a redox reaction. The standard reduction potential of hydrogen is 0 volts.

Among the given options, the elements that can produce hydrogen in an alkaline medium are those with a higher reduction potential than hydrogen. Let's evaluate each option:

A) Zn (Zinc) - Yes, it can produce hydrogen in an alkaline medium.
B) Cu (Copper), Ag (Silver) - These metals typically do not produce hydrogen in alkaline medium.
C) Cu, N2 - Nitrogen gas (N2) cannot produce hydrogen.
D) Al (Aluminum), C (Carbon) - Neither aluminum nor carbon typically produce hydrogen in alkaline medium.

So, the correct option is (A) - Zn (Zinc).