The correct option is D 16
Let a,b,c and d be four distinct primes.
Then the factors of a×b×c×d are:
1,
a, b, c, d (One prime at a time),
a×b, a×c, a×d, b×c, b×d, c×d (Two primes at a time),
a×b×c, a×b×d, a×c×d, b×c×d (Three primes at a time), and
a×b×c×d (All four primes) - 16 in total.