I have read the question several times and I believe "A.The kelp draws nutrients from the water rather than the soil, which it does not have available." would be your answer.
Although it is true that kelp is temperature sensitive, the question states that "They use a temperature regulation system to keep the water temperature at about 12°C." So even with the added addition of sunlight, I think the temperature still stays generally the same. And as long as the temperature is between 5-20 C degrees, the kelp should be okay.
However, kelp does not work the same as most land plants, kelp does not have a root system. It instead has a "holdfast" anchoring system that does not transport nutrients. So how does kelp get nutrients? From the water directly. Since the question says nothing about nutrients in the water, and directly talks about nutrients in the soil, we can assume that their is no nutrients in the water (only in the soil). Making A our answer.
This is a copy/pasted answer from a question I also answered.
https://brainly.com/question/4540702
