What should you check to identify organizations and describe items and quantities of equipment required to perform the mission?

The correct answer focuses on the "Allowance Standard," which serves as a benchmark or reference for identifying the specific organizations involved in a mission, as well as detailing the items and quantities of equipment necessary for that mission. The Allowance Standard is crucial because it outlines the standard equipment and supplies that units need based on their mission requirements and operational guidelines. By examining the Allowance Standard, one can ensure that the equipped resources align with the expectations set for the mission, thus facilitating effective planning and execution.

The other options, while relevant to mission planning and execution, do not provide the same level of specificity regarding equipment requirements. Operational Guidelines might offer overarching directives for conduct but lack the detailed inventory specifics. Resource Allocation addresses where and how resources are distributed rather than the specifics of what is needed. Mission Specification outlines the goals and objectives of the mission but does not typically break down the equipment needed. Therefore, the Allowance Standard is uniquely focused on the identification and quantification of necessary equipment in the context of mission execution.