Concept:Dictionary order is decided by comparing letters from left to right after the common prefix.Explanation:All given words start with the common part "Life".In Lifeless, the letters after "Life" begin with "le".In Lifelike, they begin with "li".Since "e" comes before "i" in the alphabet, Lifeless comes before Lifelike.The other options come later because "Lifespan" has "s", "Lifelost" has "o", and "Lifework" has "w" in the deciding position.So the missing first word is Lifeless.Answer:A. Lifeless