sentence: Joseph has a lot more whiteheads on his face than Joel does because 
complete: Joel is past puberty.

sentence: Rachel was the designated understudy when Victoria lost their voice due to laryngitis, so 
complete: Rachel had to decline the soprano position.

sentence: At the computers, Natalie was working on logo designs and Samantha was analyzing data in spreadsheets, because 
complete:
Natalie was a graphic design major.