Cai tried to prove that \triangle FGH\cong \triangle HIJ△FGH≅△HIJtriangle, F, G, H, \cong, triangle, H, I, J. Statement Reason 1 FG=HI=6FG=HI=6F, G, equals, H, I, equals, 6 Given 2 FH=HJ=4FH=HJ=4F, H, equals, H, J, equals, 4 Given 3 \overline{FG} \parallel \overline{HI} FG ∥ HI start overline, F, G, end overline, \parallel, start overline, H, I, end overline Given 4 \angle HFG\cong\angle JHI∠HFG≅∠JHIangle, H, F, G, \cong, angle, J, H, I When a transversal crosses parallel lines, alternate interior angles are congruent. 5 \triangle FGH\cong \triangle HIJ△FGH≅△HIJtriangle, F, G, H, \cong, triangle, H, I, J Side-angle-side congruence What is the first error Cai made in his proof? Choose 1 answer: Choose 1 answer: (Choice A) A Cai used an invalid reason to justify the congruence of a pair of sides or angles. (Choice B) B Cai only established some of the necessary conditions for a congruence criterion. (Choice C) C Cai established all necessary conditions, but then used an inappropriate congruence criterion. (Choice D) D Cai used a criterion that does not guarantee congruence

<HFG ≅ <JHI because they are corresponding angles, therefore: A. Cai used an invalid reason to justify the congruence of a pair of sides or angles.

What are Corresponding Angles?

When two parallel lines are crossed by a transversal, the angles that are formed in matching corners along the transversal are regarded as corresponding angles which are congruent to each other.

In the proof, HFG and JHI are corresponding angles that are forrmed. Therefore, they are equal based on the fact that corresponding angles are congruent.

Thus, Cai's first error in the proof was made in his 4th statement. <HFG ≅ <JHI because they are corresponding anglles, therefore: A. Cai used an invalid reason to justify the congruence of a pair of sides or angles.

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