"a" is the most probable answer but needs some elaboration.
Spiders eat their food through a process called external digestion. The gut, intestine and esophagus of a spider are designed to take in mostly liquids. The spider regurgitates digestive fluids onto the prey to digest it working more or less as a tenderizer. Once the prey begins to liquefy, it is chewed with the jaws (chelicerae) and the fluid is sucked back into the mouth together with some liquefied "'meat" from the prey.
The spider repeats this process as often as necessary to digest and ingest all but the inedible hard parts.