Once the U.S. government opened its domestic markets to international trade, the competition from imported cars, steel, and other products caused demand for similar U.S. goods to

b. fall, leading to lower output, fewer workers, and an overall decline in union membership.

Explanation:

Once the US Government opened up its market to international trade, the competition from imported cars, steel, and other products caused demand for similar U.S. goods to fall. This happened because people started importing more goods from outside as they were cheaper than the goods produced in the US. Chinese steel for instance, did not have the same high labor input costs as US steel and so could be sold at cheaper levels.

As a result of less people demanding US products, the companies had to reduce output to reduce the losses they were making. This led them to let some of their workers go and as the people were no longer working, Unions lost members.

Several vaccines are made by taking toxins and inactivating them with a chemical (the toxin, once inactivated, is called a toxoid). By inactivating the toxin, it no longer causes disease. The diphtheria, tetanus and pertussis vaccines are made this way.