What form of deductive reasoning is used in this argument?

If a triangle is scalene, it has no sides the same length.
If a triangle has no sides the same length, then it isn’t equilateral.
If a triangle is scalene, then it isn’t equilateral.

A.
law of detachment
B.
law of syllogism
C.
law of contrapositive
D.
law of converse
E.
identification of counterexample