The term carcinogen refers to: a
the spread of disease.
b
the chemicals used to stop the spread of cancer.
c
a term that means the same as an aneurysm.
d
a substance that produces cancer.

Me with this i need to get the answer quickly.

[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.

How do you imagine the heart of a person with prolonged high blood pressure might look different from the heart of someone with normal blood pressure?