Concept:Training yam vines means supporting them on stakes or trellises to expose the leaves to more sunlight.
Explanation:When yam vines are trained, the leaves do not lie on the ground in tangled masses.
Instead, they are spread out and receive better sunlight.
Greater light exposure allows the leaves to perform more photosynthesis.
This leads to increased food production, which improves the growth and yield of the yam.
Among the options given, the main purpose of training is to improve light interception and thus boost photosynthesis.
Answer:C. increase photosynthesis