Why is StartRoot 225 EndRootequals15​?

Question

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Part 1
A.
StartRoot 225 EndRootequals15 because 225 is a multiple of 15
B.
StartRoot 225 EndRootequals15 because ​(15​)(15​)equals225
C.
StartRoot 225 EndRootequals15 because both 15 and 225 are odd whole numbers

Answer 1

B. StartRoot 225 EndRootequals15 because ​(15​)(15​)equals225