“I never know," Harry called to Hagrid over the noise of the cart,
"what's the difference between a stalagmite and a stalactite?" (Harry
Potter and the Sorcerer's Stone)
There comes direct question after ‘I never know’. If it were indirect question, would it be ‘I never know what the difference between a stalagmite and stalactite is.’?
Best Answer
Yes, that's right. The quote introduces a direct question with I never know:
You've turned it into an indirect question (a wh-relative clause):
The main difference is that the indirect question doesn't take the form of a question grammatically, so it doesn't undergo subject-auxiliary inversion, and it ends with a period rather than a question mark. The other difference is that the original sentence, containing a direct question, can contain a comma between the matrix verb and its complement; see this answer for a description of that structure.