Which of the following is not a resource found in the north sea? fish oil pearls natural gas

The correct answer is - pearls.
There's no clams that make pearls in North Sea. It is well know for it's reserves of oil and gas, mainly used by Norway, and in smaller amount by the United Kingdom, and it was the biggest reason why Norway's economy flourished in the past decades. Also the fishing is very important and there's plenty of fish, and again Norway is the leader in that department.