题目选项分析

A nuclear test explosion was detonated recently in the Pacific Ocean, creating a substantial blast with a yield of 7.3 kilotons, or magnitude 5.1 on the Richter scale if it had been measured as an earthquake.

A nuclear test explosion detonated recently in the Pacific Ocean created a substantial blast with a yield of 7.3 kilotons; an earthquake with that force would measure as magnitude 5.1 on the Richter scale.