It would 3 because if you read it tells you the answer
I think the answer would be A because O is oxygen and it has 7. Although it’s in parentheses and has a 2 on the outside of those parentheses, so you would multiply and 7 x 2 = 14. 14 is larger than the other ones.
Hopefully I’m right and hopefully that helps.
First read the introduction.
Seconds look at the pictures how to build it.