Here's a problem to solve: A morning glory is a type of flowering vine that climbs trees and fences. Which of the following behaviors most helps a morning glory plant climb a fence?

Among the 4 following options, which is the correct answer?

- A: stems curling in response to touch
 
- B: stems swelling in response to water
 
- C: flowers opening in response to light
 
- D: roots growing in response to gravity
 