We've been going through the multiple-choice questions in Chess Choice Challenge, and some we have done quite quickly. But this one took us most of a session to talk about!
We struggled a bit with 'unnecessary' -- surely none of are actually 'necessary'? But maybe some of them are good and some of them are bad. Try and decide for yourself before reading on!
1. 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5.d4 Be7 6. Bd3 Nf6 7. h3 -- a good move, keeping Black's Bishop on c8 from finding a good square
2. 1. e4 e5 2. Nf3 Nc6 3. Bc4 h6 -- a bad move -- Ng5 is not a threat now and won't be next move either (even if your next move is 3...Nf6, but you have to know that one)
3. 1. e4 d5 2. exd5 Qxd5 3. Nc3 Qa5 4. d4 Nf6 5. Nf3 Bg4 6. h3 -- a good move, forcing the Bishop to make up its mind -- we get the Bishop pair (6...Bxf3) or King's-side space (6...Bh5 7.g4)
4. 1. d4 Nf6 2. c4 g6 3. Nc3 d5 4. Nf3 Bg7 5. Bg5 Ne4 6. cxd5 Nxg5 7. Nxg5 e6 8. Nf3 exd5 9. e3 O-O 10.b4 -- a move that is part of a good plan, the minority attack, hoping to make use of the half-open c-file. (That needs a good 10-minutes of explanation if you haven't heard of it before!)
So, only 2 is bad, so we decided the answer was C. That was hard work!