[Q]: How does the sentence end?

Mary asked Rebecca what the chemical symbol for nitrogen was because 

[A]: Mary could not remember.


[Q]: How does the sentence end?

Laura wanted Natalie to hang a hammock in the backyard because 

[A]: Laura is shorter than the other.


[Q]: How does the sentence end?

It was easier to teach the students to configure the server than the router because the 

[A]:
router was complex.