Which of the following are pairs of equal sets?

Equal Sets = Two sets A and B are said to be equal if they have exactly the

 same elements & we write A = B

We have

$C=$ set of letters in the word, 'CATARACT.'

$\mathrm{C}=\{\mathrm{C}, \mathrm{A}, \mathrm{T}, \mathrm{R}\}$

and $D=$ set of letters in the word, 'TRACT.'

$D=\{T, R, A, C\}$

Here, C = D because the elements in both the sets are equal. The repetition of elements in a set does not change a set.

Thus, $C$ and $D$ are equal sets.