A US Boycott Against Mexican Tuna Caught in Nets Was

A U.S. boycott against Mexican tuna caught in nets was:

A) not upheld by the WTO on the grounds that killing dolphins in tuna nets does not harm the U.S. directly.
B) upheld by the WTO on the grounds that nations can impose any environmental standards on other nations.
C) upheld by the WTO on the grounds that the use of nets to catch tuna also kills dolphins.
D) not upheld by the WTO on the grounds that U.S. ships could still use nets to catch tuna.