Answer: BC = EF (third choice)
Reason:
SAS = side angle side
The tickmarks show that AB = DE is one congruent pair of sides. This takes care of one "S" of "SAS". It doesn't matter which "S".
The "A" of "SAS" is handled by the marked congruent angles B = E.
The missing info we need is the other "S" of "SAS".
If we knew that BC = EF, then we'd have enough information to use SAS. Take careful notice that the angles are between the sides mentioned.
