Which of the following types of major contamination is NOT likely in a nuclear attack?

In the context of a nuclear attack, different types of radiation can result from nuclear fission and decay processes. Neutrons are typically associated with specific nuclear reactions, such as those in nuclear reactors or during initial fission events. In a nuclear explosion, the immediate concern is primarily the release of radiation that directly affects those in the vicinity, which includes alpha particles, beta particles, and gamma rays.

Alpha particles are heavy and can be stopped by a sheet of paper or even skin, but they can be dangerous if ingested or inhaled. Beta particles penetrate a bit further and can be harmful, especially to skin and eyes. Gamma rays, being high-energy electromagnetic radiation, can penetrate deeply and represent a significant external hazard.

In contrast, neutrons are not considered a major contamination type in the aftermath of a nuclear attack because they do not travel far in the atmosphere. Their interaction requires specific conditions that are more relevant to controlled nuclear reactions or certain types of nuclear devices. As a result, while neutrons may be present immediately during the explosion, they are not the primary concern for contamination in a large-scale nuclear attack scenario. This makes neutrons the correct choice as they are least likely to present as lingering contamination in such an event.