What Was the Primary Reason Why American Firms Lost Market

What was the primary reason why American firms lost market dominance in many industries in the 1970s and 1980s?

A) OPEC oil embargoes
B) the Vietnam war had drained the economy of resources
C) after Richard Nixon was President, foreign consumers began to mistrust American firms
D) they had become lax with a lack of competition in the 1950s and 1960s
E) foreign government subsidies for business