Agroup of science students has been learning how the human circulatory system reacts
during exercise. the students measured their heart rates both before and after they ran five
laps around the school gym. this was repeated two more times, with a 5-minute rest period
between each trial. the average heart rates of the students are shown in the bar graph.

 HR increases with activity and decreases when at rest. By measuring HR before and after exercise, students will be able to predict their level of cardiovascular fitness.

Explanation:

During exercise, the heart pumps at a greater frequency to supply the working muscles with blood, i.e. oxygen. After exercise, the heart does not need to pump at a high rate to supply resting muscles with the necessary oxygen.  Therefore, the HR of the students is greater during exercise and slows dramatically at rest.

Students could measure their HR at the carotid artery in the neck, on the brachial artery just under the upper arm or at the radial artery on the wrist.

answer; i believe that the correct answer is (b) is a factor associated with physical activity and heart disease;

to prevent people from getting the ebola virus, countries around the world paid to doctors develop a new vaccine. now that the vaccine has been made, doctors will need to experiment on a large number of people to find out if it works safely.

what is the greatest limitation that scientists are dealing with as they try to figure out how to experiment with the ebola vaccine?

meditation is a practice of sitting still and quiet for minutes or even hours. it has been practiced for thousands of years and is even a part of religious practices for some people. carefully controlled, repeated measurements of brain activity have shown that meditation does increase certain chemicals in the brain and even grows the part of the brain that people connect with their current surroundings and activities.

are claims about the effects of meditation most likely scientific or pseudoscientific?

not pseudoscientific, because people have made claims about it but scientific observations have not been made