QID 400848:

Marking three notes on this one. Wasn't sure how to go about annotating that, but noting it here in case there is a specific workflow that is desired, so I know how best to do it moving forward. :-)

One note defines white blood cells as being leukocytes, which is how they are referred to in the question.

The other card/s define the location of origin for leukocytes as being in the bone marrow, which is a necessary discriminator in the question and, in this case, the sole fact necessary to get the question right because it is phrased as an "everything except" style question, and so knowing that the origin for leukocytes is in the bone marrow (rather than the kidney) is necessary and sufficient to correctly answer the question.