I would probably say d because Intraspecific competition is an interaction in population ecology, whereby members of the same species compete for limited resources. This leads to a reduction in fitness for both individuals, but the more fit individual survives and is able to reproduce.
The answer would be serratus anterior.
Sentence form: The serratus anterior muscle is important in thrusting movements of the arm, much like a boxer's jab punch.
This would be advantageous under cold conditions because the roots could continue to grow though the rest of the plant is frozen off