Which statement is a true statement? Agency agreements

Question 3 options:

a)	are agreements of utmost good faith on the part of the agent.
b)	may only be terminated by notice given, or by the death, insanity, bankruptcy of either principal or agent.
c)	would not include, by definition, Powers of Attorney.
d)	if arising other than through operation of law or by necessity, must be in writing to be valid.