A business plan is a formal statement of a set of business goals, the reasons they are believed attainable, and the plan for reaching those goals.
句中的thereasons they are believed attainable在从句中干什么成份？
A business plan is a formal statement of a set of business goals, the reasons they are believed attainable, and the plan for reaching those goals.
句子主干：
A business plan is a formal statement of A, B, and C.
A,B,C分别是句中的a set of business goals，the reasons they are believed attainable，和the plan for reaching those goals
其中the reasons they are believed attainable，即the reasons [why] they are believed attainable
