Which indicator would best support the claim that government policies have had a positive effect on U. S. GDP over the last 30 years?

A. change in the U. S. balance of trade compared to the change in GDP

B. change in federal funding of technological research compared to the

change in GDP

C. change in external debt over time compared to the change in the

U. S. balance of trade

D. change in GDP over time compared to the change in the U. S.

balance of trade