Which two sentences convey the same idea?
1) Shouldn’t they have checked your tickets?
2) I wonder if they should have checked your tickets.
3) I want to know if they checked your tickets.
4) They should have checked your tickets.

Sentence 1 implies that the speaker feels that the tickets should have been checked.

Sentence 2 implies that the speaker is wondering whether the tickets should have been checked.

Sentence 3 implies that the speaker is asking whether the tickets were checked.

Sentence 4 implies that the speaker feels that the tickets should have been checked.

Thus, 1 and 4 convey the same meaning.

Hence, the answer is option C.