A _____ consists of two or more targets on which fire is desired simultaneously.

A term that describes two or more targets on which fire is desired simultaneously is best defined as a "Group of Targets." This term encapsulates the concept of treating multiple targets as a single unit for the purpose of fire support, allowing for coordinated engagement strategies to maximize the effectiveness of combat operations.

Using the term "Group of Targets" signifies that these targets need to be engaged at the same time, creating a focused impact on the battlefield. This approach is crucial for maintaining tactical advantage, as it increases the chances of neutralizing opposing forces efficiently.

The other terms, while potentially related, lack the specificity or recognition within military doctrine. For instance, "Collective Target Set" usually refers to a broader grouping or catalog of targets rather than a simultaneous engagement. "Series of Targets" may imply a sequential engagement rather than simultaneous, and "Multiple Targets" is a general term that doesn’t necessarily convey the coordinated action intended in the context of fire support operations.