Tips for spotting size difference in keyhole?

[Bigbirdo]

Hello, guys, I am working on the Bootcamp keyhole practice test right now. How do you guys usually spot the size difference (like which one is higher, bigger) between the given key and the answers? What signs should I look for?

 

[NMC2010]

It's just something that takes practice practice practice. I usually look for differences in the proportions of the answers and compare the differences to the original.