What type of compound releases oxygen readily and can cause fires when in contact with combustibles?

The most appropriate choice in this case is the organic peroxide. Organic peroxides are a class of compounds characterized by the presence of a peroxide functional group (-O-O-). This structure grants them the ability to release oxygen readily, making them strong oxidizing agents. They can initiate combustion and often cause fires when they come into contact with combustible materials due to their ability to provide oxygen, which is essential for combustion.

In many cases, organic peroxides are used as initiators in polymerization processes or as bleaching agents, but their reactive nature also means they pose significant hazards. They can decompose exothermically, leading to rapid combustion under certain conditions, particularly if they are not properly handled or stored.

Oxidizing agents and oxidizing materials also release oxygen; however, the term "oxidizing material" can encompass a broader range of substances beyond just organic peroxides. Not all oxidizing agents exhibit the same level of risk as organic peroxides when it comes to combustibles. Meanwhile, combustible liquids are primarily fuels themselves and not necessarily expeditors of oxygen. Therefore, organic peroxides are specifically notable for their propensity to promote fires in the presence of combustible substances due to their inherent chemical properties.