Because you're kind of expecting to write plurals I kind of agree with only accepting them (similar to people preferring Pittsburg without the h not being accepted)
I put mm for the 50 Cent question. Because that was the caliber of the bullet. I guess technically he wasn't struck by a 9mm because that would refer to the gun, not the bullets.
Wow, I think “Inch Nails” should’ve been counted, same with “Symphony” in singular since it’s the 9th Symphony. Anyway, I didn’t like this quiz’s criteria — one star.
Also 'inch nails' is not accepted.
Beethoven wrote his "9th Symphony" or "Symphony #9".
It is a slightly different, but equally valid, answer.