He refused the invitation to dinner on the ______ of being too busy.

A．some of the highest pesticide residues appear in meat and eggs
B．a meatless diet does not provide enough nutrients
C．protein can be found in almost every food
D．more than 80% of the corn in the United States are fed to livestock

A．They feel that eating animals is unethical.
B．There are fewer livestock available due to the environmental pollution.
C．The consumption of meat will lead to financial problem.
D．Being a vegetarian is beneficial to the protection of water.