[Q]: How does the sentence end?

The computer was stumped by the algorithm but solved the equation with ease, as the 
OPTIONS:
- algorithm was so simple.
- equation was so simple.

[A]: equation was so simple.


[Q]: How does the sentence end?

The girl put the history book back on the shelf and read the magazine because the 
OPTIONS:
- book was boring.
- magazine was boring.

[A]: book was boring.


[Q]: How does the sentence end?

Mary left the envelopes in the basket and focused on addressing the postcards, because the 
OPTIONS:
- envelopes were nonurgent.
- postcards were nonurgent.

[A]:
envelopes were nonurgent.