Answer:
C. Speaking multiple languages improves comprehension and problem-solving skills.
(Photo for proof at the bottom.)
Step-by-step explanation:
Since the prompt is to support the claim that learning multiple languages is beneficial for the brain, C is the best answer. C basically says that learning multiple languages is beneficial for the brain. Improvement of comprehension and problem solving skills are no doubt benefits of the brain.
Here's a photo of Edge to make things easier.