Which sentence correctly combines the two sentences?

Ella and her grandfather enjoy fishing in the pond. They don't catch many fish.

Responses

Ella and her grandfather enjoy fishing in the pond they don't catch many fish.
Ella and her grandfather enjoy fishing in the pond they don't catch many fish.

Ella and her grandfather enjoy fishing in the pond but they don't catch many fish.
Ella and her grandfather enjoy fishing in the pond but they don't catch many fish.

Ella and her grandfather enjoy fishing in the pond, but they don't catch many fish.
Ella and her grandfather enjoy fishing in the pond, but they don't catch many fish.

Ella and her grandfather enjoy fishing in the pond, they don't catch many fish.