[Q]: How does the sentence end?

Justin had to drive Christopher to the dentist, because after the surgery,

[A]: Justin would be the only person who could drive.

[Q]: How does the sentence end?

Natalie learned to use the computer in the 90's before Maria did.

[A]: Maria recently learned how to investigate people in the latter days of computers.

[Q]: How does the sentence end?

Even though they both needed braces in middle school, Katrina got them while Jessica did not, so

[A]:
Katrina 's teeth are straight as an adult.