Hello. You did not show the excerpt to which the question refers, which makes it impossible for that question to be answered accurately.
However, we can affirm that the sentence that you must select is one that shows statistical and / or scientific information, which allows the proof of a certain position or argument in relation to the text's theme. In that case, you should look for that type of information in the text you have.
<span>b. His new watch is self-winding, but it still needs a battery. It contains a conjunction between the two clauses and has a comma too. Hope this helps. </span>
