A program runs `a = [1]`, `b = a`, and `b.append(2)`. What is `a`?
`[1]`, because assignment deep-copies lists
`[2]`, because append replaces the old contents
`None`, because append returns no value
`[1, 2]`, because both names refer to one list✓پاسخ درست
توضیح
Assignment copies the reference, not the list, so `a` and `b` designate the same mutable object. Appending through either name is therefore visible through the other; a separate `[1]` would require an explicit copy.