L is NPC, so by definition L belongs to NP and every problem in NP reduces to L in polynomial time. Options A and B are True,
$A_{TM}$ describes the famous Halting problem which is undecidable.
Undecidable languages are harder than decidable languages (P and NP), hence, every problem in NP is polynomial time reducible to $A_{TM}$
But, the converse is not true. Harder problems can't be reduced to easier problems in polynomial time.
Hence, C is True, but D is False (Answer)
$A_{TM}$ is undecidable. NP and P are the subdivisions of the decidable zone. Undecidable isn't included in it. Option E is True.