Detailed Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Problem:Passage: Cephalochordata: Cephalochordates include the lancelets ( Figure below ), fish-like marine animals often found half-buried in the sand. Cephalochordates have a notochord and nerve cord but no backbone. Answer: backbone
Solution:
Cephalochordates have a notochord and nerve cord but not a?