With a question like this, I kept thinking based on my knowledge of the nature of saline solution, and I thought that the temperature could be lowered to any extent. Therefore, the answer becomes -2C, which it is possible for saline solution to drop to at that concentration. I had considered only to the physical function of water, and forgot the fundamental part, the actual condition of ocean water. And also, there were several experiments that I thought were interesting, which were not hypothetical experiment class problems. There was one on the mechanism of microwave ovens, in which only water reacts.
Water has polarity so it can be heated in a microwave oven.
He asked, well then, what will happen if you put in metal. The professor did interesting experiments for us, such as when he took a chemical reagent which the police use when they are to detect bloodstains, and when he added a blood-like substance to it, it emitted a pale blue light. He also froze flowers with liquid nitrogen. He would do such experiments for us, which would give us a little breather. But these are not only interesting, they are all related to water.