Which Statement Best Describes the Operation of a NGT- Triggered

Multiple Choice

Which statement best describes the operation of a NGT- triggered D flip- flop?

A) The Q output is always identical to the D input.
B) The Q output is always identical to the CLK input if the D input is HIGH.
C) The Q output is always identical to the D input when CLK makes a PGT.
D) The logic level at the D input is transferred to Q on NGT of CLK.