Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: A researcher is viewing a cell that has cell walls. To best narrow down the taxonomic group from which the cell belongs, which question should a researcher ask?
What is the composition of the cell walls?
Which kingdom does this organism belong to? (Plants)