A student hypothesized that watching sports on television would cause viewers' pulse rates to increase. She designed an experiment to determine the effect of watching sports on pulse rate. A group of 200 volunteers took their pulse rates and then watched their favorite sports on television. After the games, they immediately took their pulse rates again. The data collected showed that the pulse rates of some people increased, but the pulse rates of an equal number of people did not change. Although the hypothesis was not supported by the data, the hypothesis is still valuable because it 1. may lead to further investigation 2. can be changed to fit the data 3. is the opinion of the experimenter 4. is based on beliefs of the volunteers

A single-celled organism has organelles called contractile vacuoles to move water from inside to outside the cell. The data presented in the table above were obtained in an experiment in which an organism was placed in water with different salt concentrations. The rate at which the contractile vacuole contracted to pump out excess water was recorded. How could you explain the observed relationship between the rate of contractile vacuole contractions and the salt concentration? A. When the salt concentration outside the cell is very high, diffusion causes water to move inside the cell, and the contractile vacuole has to contract more rapidly. B. When the salt concentration outside the cell is very low, diffusion causes water to move outside the cell, but it has no impact on the contractile vacuole contractions. C. When the salt concentration outside the cell is very high, diffusion causes water to move outside the cell, and the contractile vacuole does not need to contract as rapidly. D. When the salt concentration outside the cell is very low, diffusion causes water to move outside the cell, and the contractile vacuole does not need to contract as rapidly.