Why do some teenagers have late puberty?

Why is sustainable agriculture so important?

Practice or pre-exercise theories of play pose the idea that a. play provides children with an opportunity to practice adult activities. b. play is necessary to reenergize human cognition. c. children have too much energy and play will rid them of that energy. d. children are the link between animals and human beings.

[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.