Which statement is true about this argument?

premises:

if a triangle has three sides of equal length, then it is an equilateral triangle.

the side lengths of △def

are 3 cm, 3 cm, and 3 cm.

conclusion:

△def

is an equilateral triangle.

a.) the argument is not valid because the conclusion does not follow from the premises.

b.) the argument is valid by the law of syllogism.

c.) the argument is valid by the law of detachment.

d.) the argument is not valid because the premises are not true.