If the Local Chapter of the Canadian Diabetes Association (CDA)sponsors

If the local chapter of the Canadian Diabetes Association (CDA) sponsors a free lifesaving course,city residents will not have to pay to take the class.Why will an exchange take place?

A) The CDA does not have to communicate with class participants.
B) People who take the course have to give nothing of value in return.
C) Both the CDA and the people taking the course will trade something of value.
D) People can decide the course has no value.