Because it is the verb form of antworten for 3rd pers. sg. in present tense.
That is not a valid sentence though, since "Antwortet" is not a noun. When talking with real people you need to be able to correct in your head if they accidentally say "The any cows?" instead of "See any cows?"
Gee, get one letter wrong and it counts against you. Didn't used to. I put a d instead of the second t. Unless of course there's entirely different word that uses a d instead of the t in the middle.