You need to answer a given question containing a blank (_). Your answer must be one of the two objects mentioned in the question, for example "trophy" and "suitcase". Your answer must not contain a word that is not present in the question. Please don't use articles (e.g., the, a) before the answer.

[EX Q]: Andrew took notes and asked his teacher lots of questions in class, and he thought that the _ helped him prepare for the test.
[EX A]: notes

[EX Q]: He used a harness instead of a collar on his dog because the _ didn't choke the dog when it pulled.
[EX A]: harness

[EX Q]: Paul couldn't decide between a android or iOS device but chose an android because the _ was closed-source.
[EX A]:
iOS