Concept:A major flaw of Nigeria’s 1962–1968 National Development Plan was its heavy reliance on external funding.Explanation:The 1962–1968 plan was one of Nigeria’s first post-independence development plans.It was widely criticized because its execution depended mainly on foreign-sourced financial resources rather than domestic revenue.This made the plan vulnerable to external influence and unsustainable.Answer:D. its execution was based largely on foreign-sourced financial resources