Which of these sentences are grammatically correct?
1. How do you think has he done it?
2. How do you think he has done it?
Please elucidate!
1. * How do you think [ has he done it ]? 2.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
1. *How do you think [has he done it]?
2. How do you think [he has done it]?
2. is correct. In your example, subject-auxiliary inversion is only permitted in the matrix (main) clause, not the bracketed embedded subordinate clause as well.
Think of it like this: