Korean Political History II: Chapter 6, Exercise 2 — Possible Solution
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QUALIFICATION
About 60 warheads is the source's estimate as of 2025, with capacity to add
6 to 7 a year. It is an outside estimate, and the source does not say who
made it or how.

REWRITE
"One source estimates North Korea has about 60 nuclear warheads as of 2025,
the world's smallest stockpile, though such counts cannot be verified from
outside."

CAUTION
I did not research other estimates.