题目选项分析

By 1940, the pilot Jacqueline Cochran held seventeen official national and international speed records, earned at a time in which aviation was still so new such that many of the planes she flew were of dangerously experimental design.

By 1940, the pilot Jacqueline Cochran held seventeen official national and international speed records, earned at a time when aviation was still so new that many of the planes she flew were of dangerously experimental design.