The correct answer would be the second option. The correct plan for his experiment would be that the temperature, the type of limestone, and the type of acid are controls. The amount of acid and the amount of damage to the limestone are variables. To determine the degree of damage of the acid it would be best that the amount of acid is the manipulated variable while everything else are assumed constant.
Answer:
college undergraduates are not typical of the public at large
Explanation:
"Patrick Moore", who hosted the BBC program "The Sky at
Night" for more than 50 years; and just missed one episode.
He missed just a single episode when he was sick because of
an episode of food poisoning. Moore was a productive author on space science
whose exploration was utilized by both the U.S. and the Soviet Union in their space
programs.
