Factor t12 – r3s15.

Rewrite t12 – r3s15 as (t4)3 – (rs5)3. Apply the difference-of-cubes rule, x3 – y3 = (x – y)(x2 + xy + y2), with x = t4 and y = rs5. This gives (t4 – rs5)(t8 + rs5t4 + r2s10), which is choice B.

AI-written and checked against the verified answer.