In the following question, there is a sentence which is divided into four parts. Choose the fragment that carries an error (if any). Ignore punctuation errors if any.
The topography of the ocean floors / is not too well known, / since in the greatest areas the available surroundings are / often hundreds or even thousands of miles away.
since in the greatest areas the available surroundings are
The error is in the section 'since in the greatest areas the available surroundings are'.