Final answer:
The Communist Control Act of 1954 was the legislation passed to ban communist candidates (option a) from participating in national public office, targeting the Communist Party USA during the Cold War.
Step-by-step explanation:
The legislation that was passed to ban communist candidates from participating in national public office is the Communist Control Act of 1954. This act was written in response to the heightened fear of communism during the Cold War era and specifically targeted the Communist Party USA (CPUSA). The act declared the CPUSA to be part of a conspiracy to overthrow the government and banned members from working in certain industries and holding certain public offices. This law, along with others such as the Internal Security Act of 1950, was part of a broader effort to curb the spread of communism in the United States during a time when the fear of subversion was at its peak.