Researchers call random radio listeners on the phone to rank five different popular songs. This research helps radio stations decide which songs to play more often. This method of gathering data is classified as
a census.
a sample survey.
an experiment.
an observational study.

answer; (phospholipid);

sulfur dioxide

explanation: acid rain is caused by a chemical reaction that begins when compounds like sulfur dioxide and nitrogen oxides are released into the air. these substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as acid rain.

substitution is the answer in this case