For which of the following situations is a one-sample t test appropriate:

a. You want to know if the average salary for males is the same as the average salary for females. You have available a sample of male salaries and female salaries.

b. You want to know if the average difference in systolic blood pressure in a standing and reclining position is 0. You have values for differences for 50 people.

c. You want to know if the average ACT score for your school is 18.

c. You want to know if two schools have the same average ACT scores.