Studying for a certification test

And ran across this question

Which is a less than ideal example of collaboration in successful inclusion?
a) Special education teachers are part of the instructional team in a regular classroom.
b) Special education teachers assist regular education teachers in the classroom.
c) Teaming approaches are used for problem solving and program implementation.
d) Regular teachers, special education teachers, and other specialists or support teachers co-teach.

I assumed the answer was b as it is not collaboration.

The book says "b". In a special education setting, the special education teacher should be the lead teacher.

Huh?