Can someone tell what the answer is

Which step would a state health department most likely take to reduce lead exposure? promote health-planning operations to limit lead exposure at home. evaluate the number of countries affected by lead exposure. create general national guidelines for working with lead. carry out research on the worldwide effects of lead products.

Explain the sliding filament method

[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.