Jerry was terribly keyed up. In the past he had lectured Nancy on the dangers of working with Ebola in a space suit, and now he was leading a team into an Ebola hell. At the moment, he didn't care what happened to himself, personally. He was expendable, and he knew it.
Based on context clues, what is the best definition of the word "expendable”?
necessary to an operation
knowledgeable about a topic
capable of being sacrificed
useless in a specific situation