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]: The bag was used to collect some water and emptied to the pot but to out disappointment we met nothing in the pot. The _ is  watertight.
[EX A]: bag

[EX Q]: The engineer created robots to replace the algorithms at solving the puzzle. The _ were more advanced.
[EX A]: robots

[EX Q]: John changed his diet from a vegan plan to a vegetarian plan because  the _ was rigid.
[EX A]:
vegan