Answer: B. by the definition of isosceles triangle.
Step-by-step explanation:
<u>Definition of Isosceles triangle : </u>IT is a special kind of triangle that has two sides of equal length or two angles of equal measure.
Thus , if a isosceles triangle is given then its two sides must be congruent.
Given : WXY is an isosceles triangle.
Side WX and side YX are congruent <u>by the definition of isosceles triangle</u>.
Hence the correct answer is option B. " by the definition of isosceles triangle."