Answer:
Option B, Apply auxin directly to the lower part of the stem opposite from the direction you want the stem to bend.
Explanation:
Options for the question are
A) Apply auxin directly to the shoot tip on the side to which you want the tip to bend.
B) Apply auxin directly to the lower part of the stem opposite from the direction you want the stem to bend.
C) Inject compounds that block auxin receptors into the part of the stem opposite from the direction you want the stem to bend.
D) Plant the roots in two different pots, and apply auxin to the root bucket that is on the same side as the direction you want the plant to bend.
Solution
Auxin is responsible for stem elongation by inhibiting growth of lateral buds. The movement of auxin is opposite to the direction of elongation of cells. Generally, Auxin moves to the dark side which is opposite to the direction i.e the lighter side in which cell elongate . Due to this growth pattern, the stem tip gets curved towards the light.
Hence, option B is correct