What type of weapon combines harmful agents to create a devastating effect?

Each of the options refers to distinct types of weapons that can produce harmful effects, but when considering the broader category that encompasses harmful agents, the correct response is that all of them can be classified under this umbrella.

Chemical weapons utilize toxic chemicals to incapacitate or kill human targets. These weapons produce immediate effects on health through the exposure to harmful substances, causing injury or death depending on the nature and concentration of the agent used.

Biological weapons employ pathogens or toxins derived from living organisms. These agents can spread diseases which affect a significant portion of a population, resulting in high morbidity and mortality rates over time, thereby creating a more insidious form of attack.

Dirty bombs, or radiological dispersal devices, combine conventional explosives with radioactive materials. Although they don't combine harmful agents in the same way that chemical or biological weapons do, they are designed to spread radioactive contamination over a wide area, leading to long-term health effects from radiation exposure.

Given this context, all three types of weapons serve the purpose of causing harm and have the potential to create devastating effects. Therefore, stating that each of the options involves harmful agents aptly reflects the varied ways in which such weapons can manifest their destructive capacities.