Factor t12 – r3s15.

Rewrite the expression as (t^4)^3 − (rs^5)^3. Apply the difference-of-cubes rule, a^3 − b^3 = (a − b)(a^2 + ab + b^2), with a = t^4 and b = rs^5. This gives (t^4 − rs^5)(t^8 + rs^5t^4 + r^2s^10), which is choice B.

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