Linda works for a Section $501($c$)(3)$ organization that sponsors a Section $403($b$)$ plan. Which of these statements regarding a Section $403($b$)$ plan is CORRECT?

A$)$

$403($b$)$s do not allow a worker to elect to treat employer contributions as Roth contributions.

B$)$

A special catch$-$up provision available for Section $403($b$)$ plan participants allows the elective deferral amount to be doubled in the last three years before the plan's normal retirement age.

C$)$

Funding in the plan is essentially limited to annuity contracts or mutual funds.

D$)$

Because the organization is a nonprofit, employer contributions to the plan are currently taxable to the employees.