(2) The experiments we do are generally controlled experiments, so it is required that ① form a control and ② the variables are unique. In the designed experiment, we obviously found that the experimental design was not controlled. As a control experiment, we should ensure the uniqueness of variables. Because the experiment explores the effect of acid rain on plant growth, the only variable should be acid rain. Set another pot of soybean seedlings with the same conditions and spray water every day.
(3) Spray the soybean seedlings in the flowerpot with simulated acid rain once a day. After a few days, all the soybean seedlings in the flowerpot died. It can be found that acid rain has a bad effect on the growth of plants.
(4) In experiments, we usually use multiple seeds, such as 10 seeds, to avoid the contingency caused by too few seeds (own conditions, dormancy and other factors).
(5) In order to make our living environment better, we have many measures to prevent acid rain, such as coal desulfurization, replacement with clean energy, tail gas absorption and so on.
So the answer is: (1) Acid rain has an effect on plant growth (or acid rain has no effect on plant growth); (2) Set another pot of wheat seedlings under the same conditions, and spray clean water (or normal rain) every day as a control; (3) Acid rain has a bad influence on the growth of plants; (4) Unreasonable, the experiment only uses 1 seed, which is accidental and affects the accuracy of the experiment; (5) desulfurization of coal; Switch to clean energy.