Which of the following statement is correct in describing diversification and correlation to provide the framework of a portfolios total risk and return relationship. Select one:

a. Negatively-correlated assets have a correlation coefficient of 0. b. To reduce risk, uncorrelated assets are less effective than positively correlated assets. c. Diversification is considered an essential part of constructing an efficient portfolio. d. Positively-correlated assets are considered better investment strategies.