Sorry, Neil, it's actually c) somnambulism – the roots of this word come from Latin.

抱歉，尼尔，实际上应该是c)睡游症。这词源于拉语。

This is called sleepwalking, or somnambulism, and scientists are still trying to figure out exactly why it occurs.

这被游或游症，科学家们仍在努力弄清楚它发生的确切原因。