An unreliable study can occur if the
a. survey is very clear
b. survey yields consistent results
c. test administration is inconsistent
d. test participant cannot guess on test questions

An unreliable study can occur if the test administration is inconsistent. 

Looking at your choices, surveys in a study should be clear, yield consistent results and test participants should not be able to guess on the test questions. It makes a good study. 

Inconsistent administration of tests can lead to errors and the results would not be credible. 

The answer is C. 

The answer is the father was relieved, the officer was tired.