He hypothesis that a mobile compound produced in the coleoptile tip controlled its bending toward directional light was tested by p. boysen-jensen in 1893. his experimental setup is represented below. both dark and light treatment groups had intact coleoptiles as controls. the experimental groups included: coleoptiles in which the tips were removed coleoptiles that were cut with the tips separated by mica coleoptiles that were cut with the tips separated by agar boysen-jensen left one set of coleoptiles in darkness for 24 hours and one set in directional light for 24 hours and observed whether they elongated and/or bended toward the light.

The coleoptiles which tips were removed will be short and straight while coleoptiles which were cut with the tips separated by mica will be short and straight. Ceoptiles which were cut tips and separated by agar they will be tall and straight.

The set of coleoptiles which will be left in the darkness for 24 hours will be tall and bent. While the set which is in the direction of light for 24 hours will be tall and bent.

Observation is that coleoptile will grow straight if the chemical was evenly distributed and curved away from block side as if growing towards the light because dark side has the higher concentration of auxin.

the answer is d (apex) good luck : ))