Risk Management Application of Option Strategies Reading 29 EOC Question

I have a doubt in the EOC question 12. The question asks to find the largest gamma among a set of options. I know that at-the-money option has largest gamma. But, isn’t the delta also supposed to be close to 0.5 for at-the-money options?

Why does the option with strike price 67.5 has such a high delta? Is it common for at-the-money options to have a delta like 16.5?