I saw a picture of a student's test where one of the questions was "Write down Einstein's equation.", and the student answered "Einstein's equation". I know it is a joke, but is this a wrong interpretation ? Is there any ambiguity ? From the context, it is clear what the teacher is asking. If the question was "Write down Einstein." then it is clear that the answer is "Einstein". What should the question be if I want the student to answer "Einstein's equation". Is it " Write down 'Einstein's equation'. "
The English language is ambiguous. The answer is probably technically valid in a narrow parochial sense, however, in a test situation there is sufficient context for the test taker to know that that is not correct.
After all, there are a lot of people named Einstein, including several dogs I have encountered in my life. Are we to think that the equation relating number of beers drunk to frequency of bathroom visits that my drunk uncle Einstein came up with, or the trajectory necessary to catch that squirrel before it runs up the tree, calculated by Einstein the dog next door, are valid answers to this question?
So even though English is indeed ambiguous, context can reduce or eliminate this ambiguity, and in fact an understanding of that context is part of what the test is all about. So the grader would be perfectly correct in marking this answer completely wrong.
Were we to go with a trick question:
Would reasonably allow the answer given.
Einstein was a mathematician and a physicist. I assume that the wording of the question was intended to imply "Write down Einstein's most famous equation" (i.e. E=mc^2, based on the further assumption that there exists a universal consensus regarding what his most well-known equation was).
But that is not what the question actually says. Since Einstein was responsible for coming up with numerous other significant equations in the course of his career, I'd have to say that whoever thought up that question was a careless and ignorant idiot.
To cut a long answer short - the student was using a loophole and being a git.
To remove all ambiguity, the question could have read, 'What is Einstein's equation?', though, that very same student probably would have answered, 'The equation owned by Einstein.'
It was abundantly clear what the teacher wanted the student to write but, either because he/she didn't know the answer or they thought they'd put it in for a joke, that student intentionally misread the question as, 'Write the following: Einstein's equation'.