When Protagoras Says That Man Is the Measure of All

When Protagoras says that man is the measure of all things, he means that

A) it is only man, of all the animals, that has devised measures for distance, weight, temperature, etc.
B) what exists must be measured by what all men have in common.
C) there is no objective criterion available to humans by which to judge truth and goodness.
D) measuring is important to man for building all sorts of things.