题目选项分析

A middleweight black hole weighs in at roughly 500 solar masses, hundreds of times more massive than the lightweight black holes produced by the collapse of individual stars, but thousands or even millions of times less massive than the heavyweight giants that lurk in the centers of galaxies.

A middleweight black hole weighs in at roughly 500 solar masses, hundreds of times more massive than the lightweight black holes produced by the collapse of individual stars, but it is thousands or even millions of times less massive as the heavyweight giants that lurk in the centers of galaxies.