Let’s start with A. It says O must always be higher than M. This is true. O can never go on the bottom shelf: it has to go higher than L. So if FM are on the bottom shelf, O is higher.
When FM are on the middle shelf, O goes on the top shelf. It’s the only way to put O above L.
This is the scenario from the setup: placing FM on the middle shelf determines everything. It’s the only way to put O higher than L.
So, A is CORRECT. No matter where you place FM, O is always higher.
The diagram above also proves C wrong. I and F can be placed on the same shelf. The diagram likewise proves D wrong: G is lower than O.
E is wrong. We’ve seen plenty of diagrams where FM are on the bottom shelf, lower than L. The diagram below proves it.
Finally, B is wrong because G is a random variable. It’s really easy to put G above K. Here’s one example.
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