Choose the Hypotheses That Can Be Tested Using Paired-Samples T

Multiple Choice

Choose the hypotheses that can be tested using paired-samples t tests. ​

A) People living in warm countries are happier than people from cold countries.
B) Homicide rates, on average, are higher in Western counties than in Southern counties of the United States.
C) Graduates had higher average salaries 10 years after the graduation than they had 5 years after the graduation.
D) The length of life, on average, is shorter for never-married persons than for married persons who married at least once.