In one study subjects were randomly given either 500 or 1000 milligrams of vitamin C daily, and the number of colds they came down with during a winter season was noted. In a second study people responded to a questionnaire asking about the average number of hours they sleep per night and the number of colds they came down with during a winter season.

A. The first study was an experiment without a control group, while the second was an observational

Step-by-step explanation:

I think your question is missed of key information, allow me to add in and hope it will fit the original one.  

A. The first study was an experiment without a control group, while the second was an observational

study.

B. The first study was an observational study, while the second was a controlled experiment.

C. Both studies were controlled experiments.

D. Both studies were observational studies.

E. None of the above is a correct statement.

My

a. Yes, The first study was an experiment without a control group because it were randomly given either 500 or 1000 milligrams of vitamin C daily, we do not know who was given 500 or 1000.

and

The second was an observational  because we can observe about number of hours they sleep per night and the number of colds.

a

step-by-step explanation:

rurbrbrjrnrbjr

step-by-step explanation:

points a and b are equidistant from the desired line, so the line you find by using them will go through point r.

using points other than a and b will give the desired line only if they are equidistant from r. if they are randomly located, the perpendicular line you create will not necessarily go through point r, hence will not be a solution to the problem.