Answer:
Option B
Explanation:
I did a question like this a long time ago so i'm not sure if its right so sorry if its wrong
D) Guard against a short circuit electrocuting a user.
"The 4-wire setup is inherently safer and better able to prevent electrical shock, which in the case of a 220/240-volt circuit can be fatal."
Your answer is B.
The relationship between medium temperature and speed of sound is a direct relationship: when one factor increases, the other increases as is shown in graph B. The British would choose the the time of day which would give the lowest speed of sound, because this would be easiest to break. Graph B shows that the lowest speed of sound would occur with the lowest air temperature - in the morning.