Answer:
The revised version of the sentence above would be as follows: My uncle has a bowling ball; however, he seldom uses it.
Explanation:
The revised version of the sentence contains an adverb clause (however he seldom uses it). Adverb clauses, also called adverbial clauses, are dependent clauses that function as adverbs. Since they are dependent clauses they must have a subordinating conjunction to connect them to the rest of the sentence. In this case, the adverb clause has been introduced by the subordinating conjunction however (see III).
As the adverb clause is a dependent clause, it fails to stand on its own as a complete sentence (see III)
I) My uncle has a bowling ball. He seldom uses it.
II) My uncle has a bowling ball
III) *;However, he seldom uses it
