To determine which statement is true and contributes to the proof of the Pythagorean Theorem, let's analyze the relationships between the triangles formed when the altitude \( CO \) is drawn from vertex \( C \) to the hypotenuse \( AB \).
- The triangles \( \triangle ABC \) and \( \triangle AOC \) share angle \( A \).
- The triangles \( \triangle ABC \) and \( \triangle BOC \) share angle \( B \).
- The triangle \( \triangle AOC \) is right-angled at \( O \), and so is triangle \( \triangle BOC \).
Using the property of similar triangles, we can establish the following relationships:
- Triangle \( \triangle AOC \) is similar to triangle \( \triangle ABC \) since they share angle \( A \) and both have a right angle. Hence \( \triangle ABC \sim \triangle AOC \).
- Triangle \( \triangle BOC \) is similar to triangle \( \triangle ABC \) since they share angle \( B \) and both have a right angle. Hence \( \triangle ABC \sim \triangle BOC \).
Based on these observations, the correct relationships contributing to the proof of the Pythagorean Theorem are:
- \( \triangle AOC \sim \triangle ABC \)
- \( \triangle BOC \sim \triangle ABC \)
Therefore, the statement that is true is: △AOC∼△ABC.
Among the responses provided, the correct response is: △AOC∼△COB. (This can be represented as similar triangles contributing to the relationship defined by the Pythagorean Theorem, assuring that \( a^2 + b^2 = c^2 \), where \( c \) is hypotenuse.)
If the only options present are indeed the ones listed in your original question, we must pick the closest valid statement from the responses provided, considering the proof methodology illustrated.
In conclusion, the most relevant response from the options given that highlights the similarity relationships contributing to the proof is: △AOC∼△COB, triangle A B C congruent to triangle A C O.