TASK DEFINITION: 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.
PROBLEM: The pine trees were still green in December, but the oak trees were not, because the _ keep their leaves in fall.

SOLUTION: pine trees

PROBLEM: The engineer created robots to replace the algorithms at solving the puzzle. The _ were more advanced.

SOLUTION: robots

PROBLEM: Yellow is better for summer while brown is best for winter, because the _ color is lighter.

SOLUTION:
yellow