A question that is free of any grammatical or logcal errors, should be labeled 'yes', otherwise it should be indicated as 'no'. A question is grammatically correct if all its entities i.e. nouns, verbs, adjectives, prepositions, pronouns, adverbs are at appropriate position. A question is logically correct if the semantic makes sense.

Let me give you an example: Sentence: Jack played basketball after school, after which he was very tired. 
Question: How long did Jack play basketball?
The answer to this example can be: Yes.
Here is why: All entities are in appropriate position and the question makes sense, so its grammatically and logically correct.

OK. solve this:
Sentence: They then took a boat to Africa and Asia, where they went on a trip through the mountains. 
Question: How long was their trip through the mountains?
Answer:
Yes.