Let's try something, we know that the mole -=6.022xx10^23 items of stuff. For the purposes of this question, let's say the mole was a round dozen, i.e. 12 individual items.
And we rewrite the question to give:
"How many ATOMS are there in the following quantities?"
"a. ONE dinitrogen molecule";
"b. 1 DOZEN dinitrogen molecules";
"c. ONE" NO_2 "molecule";
"d. ONE DOZEN nitric oxide molecules".
So instead of the mole, I have used another VERY POPULAR collective number, the dozen. And the dozen is commonly used because I can keep a tally with my thumb and the finger joints of the ONE HAND.
And so for "a, b, c, d," I can write the answers as 2,24,3,36. Clearly d. CONTAINS the most number of atoms. Are you following me? And in the question you were asked, you replaced the "dozen" with another (MUCH LARGER) collective number, "the mole", which is specified to be equal to 6.022xx10^23. It is important that you incorporate this idea of moles into your understanding. It will save you a lot of grief.
See this answer and here for another spray.
