Which of the following is NOT a well-established risk factor for one or more types of cancer?

In a set of numbers with a mean of 10 and a variance of 9 the standard deviation is

a. 1. b. 81. c. 1.11. d. 19. e. 3.

_______________ are drugs that slow down the central nervous system

a. Opiates b. Psychedelics c. Stimulants d. Depressants