Second question please

Its bc plants can only take in so much nitrogen like compounds (nitrates, ammonium etc) to keep a stable ph level so ammonium is positively charged and nitrates are negatively charged they release hydrogen to equal the ph levels but since it’s already getting ammonium in the cycle it can’t receive more and the ratio must be compatible with the plants therefore not different.
Also, plants can’t take it in bc it needs the bacteria to break the ammonium down into a usable compound. Like nitrates.
I’m sorry if that was contradicting. I’m trying my best. :)

The answer is b hope this