What are complementary dna sequences

A and T, C and G are the complementary DNA sequences I think :)

DNA strands are complementary, meaning that the strands "match up." Certain bases can only pair with each other. A only pairs with T, and vice versa. C only pairs with G, and vice versa.

For example, say one sequence is A-T-T-C-G-A
The complementary strand would have to be T-A-A-G-C-T because A-T and C-G always go together. 

Cand d are correct because the rest are just showing your mistakes and you don’t want people who are reading a summary you wrote to see all the mistakes you made.