The "Knowledge" Described in the First Two Standards for Teaching

The "knowledge" described in the first two Standards for Teaching and Learning Mathematics refers to which of the following?

A) Administrators' knowledge of how mathematics teachers function.
B) Mathematics teachers' knowledge of the content they teach.
C) Mathematics teachers' knowledge of the students they teach.
D) Administrators' knowledge of mathematics teachers and the students they teach.
E) Mathematics teachers' knowledge of the content and the students they teach.