For the following scenarios, determine whether or not they represent paired samples.
a. Test scores for students in a biology class taught by Professor Quick are being compared to test scores in a different section of the biology class taught by Professor Quack.
b. Pulse rates for students at the beginning of class are being compared to pulse rates for the same students at the end of class.
c. The weights of 10-year-olds in 2009 are being compared to the weights of 10-year-olds in 1994.