The correct answer is letter b – “hung”!
“Hang” has a lot of meanings.
1. One is to cause (a computer system) to halt so that input devices, such as the keyboard or the mouse, do not function. In this case, we use the verbs HANG and HUNG as the past tense.
2. When HANG means “to suspend by the neck until dead”, we use different verbs: HANG -> HANGED. This verb is typical of public executions in the past. (e.g., They hanged him in the main square.)
Sources: ESL Daily Bread by Jomi Rose Carla Soriano, Image via bubblews.com.