A School District Administrator Sent a Survey to All Teachers

A school district administrator sent a survey to all teachers in the district.Only 30% of the teachers responded to the survey.Which of the following is true?
I.The people that did not responded are likely to be similar to those that did so he should Use them as the sample.
II.This survey design suffered from non-response bias.
III.Because he sent the survey to everyone, this is a census and the results can be applied to The whole population.

A) I only
B) II only
C) I and II only
D) II and III only