Justify the last two steps of the proof.?

Question

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Answer 1

it's c.

don't be fooled into thinking ST ≡ TS is symmetric property. ST and TS are different names for the same segment. a claim that the segment is congruent to itself is reflexive property. by contrast, if ST ≡ PQ, then PQ ≡ ST would follow by the symmetric property of congruence. so step 3 is reflexive, step 4 is SSS.