If abc=def, list two pairs of congruent sides and two pairs of congruent angles.

Option A

Step-by-step explanation:

Given: ΔABC≅ΔDEF

Then  by CPCTC, [ corresponding parts of congruent triangles are congruent ], their corresponding parts are congruent.

The pair of corresponding congruent sides are

AB≅DE, BC≅EF and AC≅DF

The pair of corresponding angles sides are

∠A≅∠D, ∠B≅∠E, and ∠C≅∠F

From all the given options, option A is the correct option , it shows  two pairs of congruent sides and two pairs of congruent angles.

7

Step-by-step explanation:

Divide 21 by 3 and you get 7