Rule 8 can be tested by asking two things about each proposed body: does it actually control or manage the organisation, and does the rule's wording name it.
Test 1, control:
A body triggers the bar only if it governs or manages the organisation, not if it merely advises or handles a delegated task. The General Body has no management role, it is just the collection of ordinary members. The Advisory Committee only recommends, without decision-making power. A Sub-Committee handles a narrow, delegated task rather than overall management. All three fail this test.
Test 2, wording:
Rule 8 expressly names the Executive Committee, or any board of management, as the disqualifying body.
Conclusion:
The Executive Committee passes both tests, it is the body that actually manages the organisation, and it is the body the rule specifically names.
Rule 8 exists to stop an advocate's loyalty to a client or the court from being compromised by his own stake in running an organisation he is appearing for or against. Testing each option against that underlying purpose shows why only one genuinely creates the conflict the rule is guarding against.
Only membership of the Executive Committee creates the kind of managerial stake that conflicts with independent advocacy, which is why the rule singles it out.
Therefore, the correct answer is Executive Committee.