Mathematics

Problem

A student writes the following proof: "In

\triangle ABC

and

\triangle DEF

\angle A = \angle D

AB = DE

and

AC = DF

. Hence, by ASA criterion, the two triangles are congruent." Which option best identifies the error in this proof? a)

\text{ASA requires the equality of all three angles; hence the given data are insufficient.}

\text{The triangles are actually congruent by AAS, not ASA.}

\text{The side } AB \text{ is not included between two equal angles, so ASA cannot be applied.}

\text{There is no error; the triangles have been correctly proved congruent by ASA.}