Which of the following best describes the function of the endocrine system? O A. It secretes chemical messengers that travel through the blood to signal changes at target cells B. It binds chemical messengers that travel through the blood from target cells. C. It releases electrical impulses that travel through body cells to signal changes at target cells. OD. It converts chemical messages into electrical impulses to signal changes at target cells. PLZ HELP ​

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[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.

In a two to three page paper, examine the history and development of the healthy people initiatives. discuss some of the successes and shortfalls of the three initiatives thus far; including healthy people 2000, healthy people 2010, and healthy people 2020. be sure to include statistical data from the initiatives to support your position. don't forget to cite your sources.