Vines in tropical rain forests must grow toward large trees ...

[xclash]

Vines in tropical rain forests must grow toward large trees before being able to grow toward the sun. To reach a large tree, the most useful kind of growth movement for a tropical vine presumably would be the opposite of
A) positive thigmotropism.
B) positive phototropism.
C) positive gravitropism.
D) sleep movements.
E) circadian rhythms.

[clippers!]

I chose B and got the answer, hope that helps.