Correct option is B
After GTN treatment, weekly β-hCG monitoring is done until 3 consecutive normal values, then monthly for 6–12 months to detect relapse.
Explanation of options: (a) ✘ Daily testing impractical, not guideline. (b) ✔ Correct; weekly till 3 normals = standard protocol. (c) ✘ Monthly starts only after 3 normal weekly values. (d) ✘ One-time check is unsafe; relapse may be missed.