题目选项分析

Positing an enormous volcanic explosion at the end of the Permian period would explain the presence of a buried crater, account for the presence of the element iridium (originating deep within the earth), and the presence of quartz having been shattered by high-impact shock waves.

Positing an enormous volcanic explosion at the end of the Permian period would explain the presence of a buried crater, of the element iridium (originating deep within the earth), and of quartz shattered by high-impact shock waves.