Which of the Following Best Describes an Element

Which of the following best describes an element?

A) An element is a mixture that can be separated into simpler substances using physical methods .
B) An element is a mixture that can be separated into simpler substances using chemical methods .
C) An element is a pure substance that can be separated into simpler substances using physical methods .
D) An element is a pure substance that can be separated into simpler substances using chemical methods .
E) An element is a pure substance that cannot be separated into simpler substances using ordinary physical or chemical methods.