Which one of the following statements is INCORRECT? (1 point)

A. The number of subjects in control and treatment group doesn't have to be the same in the experiment.

B. Regarding the questions sequence in survey, the classification information should be obtained first.

C. "What is your gender" is a nominal type of question in the survey.

D. Intent-to-Treat analysis is to conduct the analysis based on the initial treatment assignment.

E. In the non-probability sampling, not every element of the target population has a known chance of being selected.