Final answer:
The problem in the sentence is a comma splice, which occurs when two independent clauses are connected by only a comma. To fix it, use a coordinating conjunction or separate the clauses into separate sentences.
Step-by-step explanation:
The problem in the sentence is a comma splice. A comma splice occurs when two independent clauses are connected by only a comma, without any coordinating conjunction. In the given sentence, the two independent clauses are 'Thomas likes to surf' and 'he has no surfboard', which are connected by a comma. To fix the comma splice, you can either use a coordinating conjunction like 'but' or 'and', or you can separate the two clauses into separate sentences.