The given sentence wants to convey that based on the doctor's opinion, there is hope for recovery. The phrasal preposition 'according to' is used to express someone else's opinion. Here, the sentence is followed by a comma after the noun phrase 'to the doctors'. Therefore, it is correct. The other options either use 'according to' incorrectly or use an incorrect phrasal preposition to convey the given situation. Therefore, they are incorrect.