NEET Biology question

A simplified representation of the nitrogen cycle is given here: N2 gas in atmosphere ↔ 'X' ↔ Plant proteins → Animal proteins → 'Y' → Nitrification → N2 gas in atmosphere ↔ 'Z'.

Which of the following statements regarding 'X', 'Y' and 'Z' is correct?

• (A)'X' represents proteins which are added to the soil by the process of N2 fixation
• (B)'Y' represents ammonia which is formed by decomposition of dead plant and animal remainsCorrect
• (C)'Z' represents the process of nitrogen assimilation, by which nitrates are converted back into atmospheric nitrogen
• (D)'Z' represents the formation of nitrogen gas by putrefaction of plant and animal matter