Step 1: Identify the core issue.
The managers in the production department are burdened with additional responsibilities of financial and marketing planning, apart from production planning. They feel this is affecting their efficiency and causing delays in shipping products on time.
Step 2: Evaluate possible actions.
- (A) Creating a union: While unions protect rights, forming one might escalate conflict instead of solving the immediate problem.
- (B) Filing a lawsuit: This is an extreme step that damages employee–employer relations, and should be the last resort.
- (C) Creating a forum: This allows open dialogue between production, finance, and marketing managers, addressing misunderstandings, clarifying roles, and finding a collaborative solution.
- (D) Registering a complaint with human rights body: This is irrelevant, since the issue is managerial responsibility distribution, not human rights violation.
- (E) Going for education in the U.S.: This does not address the present organizational issue.
Step 3: Logical conclusion.
The best course of action is to create a forum for discussion. This promotes communication, teamwork, and resolution of issues in a constructive manner.
\[
\boxed{\text{The managers should create a forum for discussion and resolution of issues.}}
\]