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.

The computer was stumped by the algorithm but solved the equation with ease, as the _ was so complex.
algorithm

James went to fill up the barrel with the bucket but found that the _ was full.
barrel

I'm getting Natasha a pendant with either a diamond or amethyst gem. The _ would be best because she's an Aquarius.

amethyst