Columnist: There are certain pesticides that, even though they have been banned for use in the United States for nearly 30 years, are still manufactured there and exported to other countries. In addition to jeopardizing the health of people in these other countries, this practice greatly increases the health risk to U.S. consumers, for these pesticides are often used on agricultural products imported into the United States.

Question: Which one of the following, if true, most seriously weakens the columnist's argument?
Options:
A. Trace amounts of some of the pesticides banned for use in the United States can be detected in the soil where they were used 30 years ago.
B. Most of the pesticides that are manufactured in the United States and exported are not among those banned for use in the United States.
C. The United States is not the only country that manufactures and exports the pesticides that are banned for use in the United States.
D. The banned pesticides pose a greater risk to people in the countries in which they are used than to U.S. consumers.
E. There are many pesticides that are banned for use in other countries that are not banned for use in the United States.
Answer: "C"