The student who replies, "One; but Cruithne and other quasi-satellites and trojan moons have Earth centered orbits and could be considered moons," would probably get full credit (though I'd have some suspicion that the answer originated with the parent and not the student).
I don't understand why this answer (presumed to be originating from a parent) should get criticized by a teacher. I routinely teach my child after school. I take credit full credit for meeting my child's academic acceleration needs using my own personal time (I am not a happy camper about it because, how wonderful my life would be if the school actually met all my child's educational needs instead of making me scramble to meet them). Since this is a class test and the parent is not passing notes with these answers to the child, I would think that the teacher should accept this kind of answer and appreciate the parent and the child for learning above and beyond what the teacher was teaching (the teacher was presumably sticking to a pre-made lesson plan or 1 or 2 textbooks and a few supplements and teaching the exact same lesson to a class of 30 students with varying needs and interests).
OP: Sorry to hijack this thread trying to analyze a hypothetical test question.
