Which type of pronoun is bolded in the following sentence? cassandra, prepare yourself for some great news

Ead this sentence from the evolution of useful things.the underlined phrases indicateaaking waterproof sandpaper would allow wet sanding,which in turn would cut down on dust, and thus be a greatmprovementpassing of timea directional change of positiona cause-and-effect relationshipsequence of events.save and exitmark this and retur