John Stuart Mill Says That Humans by Nature Desire Happiness

Multiple Choice

John Stuart Mill says that humans by nature desire happiness and nothing but happiness;therefore happiness is the standard by which we should judge human conduct,and therefore the principle of utility is the heart of morality.But this argument is controversial,because:

A) it reasons from what is to what should be.
B) it has no premises.
C) utilitarianism is not a moral theory.
D) Mill failed to defend his theory.