A subjective statement is the one that is not based on facts; it is the one that is based on personal opinion, feelings or emotions. In this case, the first three sentences are facts that are scientifically proven. However, the last sentence is an opinion because everybody has a different favorite season of the year; there are no proven facts that determine which is the best season of the year. Therefore, the statement that is subjective is D: Summer is the best season of the year.