Answer:

Step-by-step explanation:
Here, we want to select the wrong option about polyatomic ions
Let us look at the options:
a) This is correct. The charge on them make them act like its a single atom
b) That is correct. The charge on them is their oxidation number
c) This is correct. They are found in combined forms, existing with other atoms or ions
d) This is incorrect. They combine with other ions of opposite charge to form molecules