In my opinion I think it's A it could be C but when you see someone around you physically see but you wouldn't call them strangers if you physically resemble and know the person. In answer a it says "emotionally disconnected" which can mean strangers but it can be temporary.
A sound of thunder tho i am not very sure why this one
You just rephrase it in your own words, but don't make the sentence too weak. Just write it in a way you would write it.
The word moon as a possessive noun is moon’s
Hopefully this helps!
An-nyŏng-ha-se-yo means hello
