Given a scientific passage and an answer, generate a question for the given answer.

Passage: With the naked eye, bacteria just look like a slimy smear on a petri dish. How can we study them in more detail? The invention of the microscope has allowed us to see bacteria, cells, and other things too small to be seen with the naked eye. Answer: slimy smear
How does the bacteria look when seen with the naked eye?

Passage: An addition reaction is a reaction in which an atom or molecule is added to an unsaturated molecule, making a single product . An addition reaction can be thought of as adding a molecule across the double or triple bond of an alkene or alkyne. Addition reactions are useful ways to introduce a new functional group into an organic molecule. Answer: an addition reaction
What is a reaction in which an atom or molecule is added to an unsaturated molecule, making a single product?

Passage: repeating bony units that make up the vertebral column of vertebrates. Answer: vertebral column
What do vertebrates possess that is made up of repeating bony units?