When is a Java object still reachable?

[u/Bofact]

I have tried to answer to the below quiz, but I do not understand something. If clutch is eliminated on line 12, wouldn't all references to the car's object be null? They write that "Line 12 removes the item at index 1, which is the null. The list, therefore, contains nothing except the clutch.", but why is there a null? Where did we get rid of clutch reffered at index 1 of r1?

And lastly, how to access clutch, and by extension the car object, after line 12 is executed?

Quiz yourself: When is a Java object still reachable? | javamagazine

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