How many diseases are prevented by vaccines?

Which of the following requires the action of a first class lever in the body

When all the values in a data set are written in order from least to greatest, the value that is in the middle, with an equal number of values below it and equal number of values above it, is called the .

Astairway has 6 steps. is it a handrail required? a. a handrail is required b. a handrail is not required c. double handrails are required d. only nosing is required