Final answer:
The correct answer is Option D. The primary distinction between a one-sample t test and a two-sample t test is the number of groups being compared.
Step-by-step explanation:
The primary distinction between a one-sample t test and a two-sample t test is the number of groups being compared. A one-sample t test compares the mean of a single group to a known value or a hypothesized value, while a two-sample t test compares the means of two independent groups.
For example, a one-sample t test could be used to determine if the average height of a group of students is significantly different from the average height of the general population. A two-sample t test could be used to determine if there is a significant difference in test scores between two separate classes of students.