Which of the following developments occurred between the fourteenth and nineteenth centuries?

[120 total points] (public health) in one of the largest human experiments ever conducted, in 1954 a randomized controlled trial was run to see whether a vaccine developed by a doctor named jonas salk was effective in preventing paralytic polio. a total of 401,974 children (ages 6–9), chosen to be representative of those who might be susceptible to the disease, were randomized to two groups: 200,745 children (the control group c) were injected with a harmless saline solution (a placebo) and the other 201,229 children (the treatment group t) were injected with salk’s vaccine.what was the point of giving saline solution to the children who didn’t get the vaccine? explain briefly.

Explain what causes the skin to burn in the sun? explain why people should avoid the sun if taking a photosensitive medication?

Annie is experiencing migraine headaches, so she visits her primary care doctor and pays with the insurance provided by her employer. what type of healthcare organization is annie utilizing?