E is sitting between D and A, B is to the right of A, C is at one of the ends and C and D are sitting next to each other. Who is sitting third?

C is at one of the ends and C and D are sitting next to each other. The two possibilities are

(1) C, D, _ , _ , _

(2) _ , _ , _ , D, C

E is sitting between D and A. The two possibilities are

(1) C, D, E , A , _

(2) _ , A , E , D, C

B is to the right of A which is not possible in possibility (2). The only possibility is

(1) C, D, E , A , B

The final arrangement is C, D, E , A , B.

$$\therefore\ $$E is sitting third in the row.

Hence, the correct answer is Option D