Question

CONGRUENT TRIANGLES

Answer 1

3.) DE

4.) C) SAS - use AC=AC - common to both triangles

Answer 2

how did you get DE for #3 @Harkirat

Answer 3

It is given that triangle ABC congruent to triangle DEF
since for congruency names have to written showing proper correspondence between respective sides, so from the name (going by sequence)
AB - DE
BC - EF
AC - DF
see attached picture