(C) Base angle theorem
Step-by-step explanation:
Given: JKLM is an isosceles trapezoid, KL ∥ JM
Prove: KM ≅ JL
Proof:
Statements Reasons
1. JKLM is an isosceles trapezoid, KL ∥ JM Given
2. JK ≅ LM definition of isosceles trapezoid
3. KL ≅ KL reflexive property
4. ∠JKL ≅ ∠MLK Base angle theorem (base=LK)
5. △JKL ≅ △MLK SAS rule
6. KM ≅ JL CPCTC
Hence proved.
therefore, option C is correct.