The road was long and hard but our spirits were unwearied.
Choose the option that best corrects the underlined part.
A comma separates independent clauses in a compound sentence that are separated by a conjunction. The comma is placed after the first clause and before the coordinating conjunction. Here, the two clauses are 'The road was long and hard' and 'our spirits were unwearied'. The conjunction is 'but'. Hence, the correct option is A.