Mary thinks the triangle is equilateral. How would you support or dispute her conjecture?

A. Calculate the slope of all three sides, and check
whether the slopes are equal.

B. Calculate the slope of all three sides, and check
whether any slopes are reciprocals.

C. Use the distance formula to calculate the length of
all three sides, and check whether all sides are
congruent.

D. Use the distance formula to calculate the length of
all three sides, and check whether any two sides
are congruent.