Question

if $\triangle abc \cong \triangle def$, then angle $\angle a \cong \angle d$ by:
\bigcirc cpctc.
\bigcirc sss congruence.
\bigcirc sas congruence.

Explanation:

CPCTC stands for "Corresponding Parts of Congruent Triangles are Congruent". When two triangles are congruent (\(\triangle ABC\cong\triangle DEF\)), their corresponding angles and sides are congruent. Here, \(\angle A\) and \(\angle D\) are corresponding angles of congruent triangles \(\triangle ABC\) and \(\triangle DEF\).

SSS (Side - Side - Side) and SAS (Side - Angle - Side) are congruence criteria used to prove that two triangles are congruent, not to state that corresponding parts of already - known congruent triangles are congruent.

Answer:

CPCTC.