Which of the Following Was Not One of Descartes' Rules

Which of the following was not one of Descartes' rules for conducting an inquiry?

A) Difficult problems should be divided into as many parts as possible.
B) Review your reasoning to make sure nothing has been omitted.
C) Reasoning should proceed from simple concepts to complicated ones.
D) Ensure that your subject is a philosophical or mathematical matter, rather than a religious or poetic one.
E) Accept nothing as true that you do not clearly recognize as being so.