Which best describes the purpose of a control sample?

Avoltaic cell converts chemical energy to

In the illustration, which two simple machines are being used to enable the student to reach the door? a. inclined plane and pulley b lever and wheel-and-axle c pulley and lever d wheel-and axle and inclined plane

Suppose astronomers built a 140-meter telescope. how much greater would its light-collecting area be than that of the 10-meter keck telescope? express your answer using two sign