Why do scientific experiments need to be repeated? A. Because scientists often make mistakes

B. To ensure that the same results are achieved every time

C. They only need to be repeated if the results are questionable

D. To discourage other scientists from trying to get the same results

B. To ensure that the same results are achieved every time

Explanation:

Scientific experiments must be repeated multiple times because scientists can make mistakes in their experiments, and so they need to ensure they get the same exact result each time they do it. Scientists may make a mistake that they do not see, so they have to B. To ensure that the same results are achieved every time.

acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.