Multiple choice general knowledge

My new colleague is a bit of a rough________but i think i'm going to like him once i get used to him

  1. stone

  2. rock

  3. diamond

  4. pearl

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

'A rough diamond' is an idiom meaning someone who may seem unpolished or harsh on the outside but has good qualities underneath. Option C correctly completes the phrase. The other stones (stone, rock, pearl) are not part of this idiom.