The Knights of Labor were the first group to try to organize unskilled and skilled labor, both men and women, and black and white, though they gave into West Coast racism and excluded the despised immigrants from Asia on the West Coast.

The statement is true

Explanation:

While the Knights of Labor were an important organization in the history of the labor movement in the United States, and have a great legacy in both labor rights achievements, and cultural matters (for example, introducing the tradition of protest songs), they where a critical part in the formulation of the Chinese Exclusion Act, which was signed into law in 1882, and prevented the Chinese from entering the United States.

The Knights of Labor were not necessarily racist against the Chinese, but they reproduced Anti-Chinese rethoric out of fear for possible displacement of American laborers due to the cheap cost of the Chinese immigrant labor force.

the answer might be either a or c. can't be too sure , because i searched the web, but no valid answers came through.

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.