Auxin can be bioassayed by Potometer, Lettuce hypocotyl elongation, Avena coleoptile curvature, and Hydroponics.

Avena coleoptile curvature test is a bioassayed (analysis of concentration or efficiency of the object by its consequence on living cells or tissues) for auxin. This test was developed by Went and is based on the polar transport of the auxin in Avena coleoptile. The edges were decapitated and auxins were dispersed to the agar blocks. Auxins diffuse only on one side of the coleoptile because the agar blocks are asymmetrically placed, as a result of this diffused side of auxin helps sides to grow and increases in the curvature of coleoptiles. The auxins sprinkled and the curvature results are directly proportional to each other. It is the most generally approved bioassay for perceptible examination of auxin concentration. So, the correct answer is option B.