Geometry

Question Analysis:
This question tests corresponding parts of congruent triangles (CPCTC) and the ability to map sides correctly based on vertex order.

Key Concept Explanation:
When two triangles are congruent, their corresponding sides and angles are equal.
The order of vertices in the congruency statement determines which parts match.

Step-by-Step Solution:
Given ΔABC ≅ ΔPQR, the correspondence is:
A ↔ P, B ↔ Q, C ↔ R.
Therefore:
AB = PQ = 7 cm,
BC = QR = 10 cm,
∠B = ∠Q = 30°.
The side corresponding to BC is QR, which must be 10 cm.

Option Analysis:
A: Incorrect. PQ corresponds to AB (7 cm), not BC.
B: Correct. QR corresponds to BC (10 cm).
C: Incorrect. PR corresponds to AC, whose length is not given.