Question about using pytest command, specifically -k option

I am current working on the Meltdown Mitigation Exercise with 4 tests to pass.
I would like to be able to run a specific test from the command line. After
spending several hours digging around the pytest documentation, I could not
find any information on how to handle specific attributes for test markers. Namely,
one uses
pytest -o markers=task
to run all the tests.
All the tests are marked with something like
My question is: How do I invoke pytest to run a specific test, say taskno=3?
‘pytest -o marker = task(3)’ or ???

Google => pytest markers => Working with custom markers — pytest documentation says to use -m to select a marker.