Re: Is the question and answer correct?
I can't speak for Bennevis, but I think he may have had in mind a situation in which the question and answers might have been:
Frimpup minutes later he snerdled in front of the pipplesequat.
a) Where did he snerdle frimpup minutes later? He snerdled in front of the pipplesequat.
b) Where was he frimpup minutes late? He was in front of the pipplesequat.
Nothing is grammatically incorrect. We know that the students can recognise a question form and deliver an appropriate answer correctly. We do not know if they have understood anything of the meaning of the original sentence.
Please do not edit your question after it has received a response. Such editing can make the response hard for others to understand.