Conventional weapons include which of the following?

Conventional weapons refer to standard armaments that are widely used in military engagements and do not include weapons classified as unconventional, such as those that cause large-scale destruction or have specific additional hazards, like chemical, biological, or radiological weapons. Submachine guns are firearms designed to fire pistol cartridges and are typically used for close combat or by military and law enforcement personnel. They fit the definition of conventional weapons due to their common usage and straightforward mechanics in armed conflicts.

In contrast, mustard gas represents a chemical weapon and is categorized as an unconventional weapon due to its specific properties and effects on human health. Similarly, radiological weapons involve radioactive materials and are classified as unconventional because they leverage radiation, rather than traditional explosive damage. Biological agents, which include pathogens or toxins used to harm or kill, also fall into the unconventional category, as they can impact populations at a larger scale and in a more insidious manner.

Thus, of the options provided, submachine guns are the only selection that aligns with the classification of conventional weapons.