We know that if you place a houseplant on a windowsill, it will soon orient its leaves toward the light. Turning the plant will cause it to orient its leaves again. Removal of the terminal bud stops this response. Which of the following is most likely the cause of this "lack of flexibility"?
A. Photosynthesis halts when the terminal bud is removed from a plant.
B. Removing the terminal bud causes the plant to produce a substance that halts movement.
C. Removing the terminal bud causes the plant to stop growing.
D. The substances utilized in response to light are produced in the terminal bud.

D. The substances utilized in response to light are produced in the terminal bud.

Explanation:

The substances which are produced in the apical meristem are known as the auxins.  are responsible for solar tracking in plants. are a powerful growth hormone that are produced naturally by plants. They are mainly found in shoot and root tips and promote cell division, stem and root growth. They also drastically affect plant orientation by allowing cell division to one side of the plant in response to sunlight and gravity. That response to sunlight by the hormone is know as phototropism where the plant would move towards the source of light which promote its growth. The movement of auxins due to gravity it is known as geotropism where the hormones moves to one side of the root in response to gravity.  

Answer is D. The substances utilized in response to light are produced in the terminal bud.

Refer below.

Explanation:

We know that if you place a houseplant on a windowsill, it will soon orient its leaves toward the light. Turning the plant will cause it to orient its leaves again. Removal of the terminal bud stops this response. Thid is most likely the cause of this "lack of flexibility" The substances utilized in response to light are produced in the terminal bud.

2%? i tried finding the exact sorry if it's not 100% correct ; -;