The correct answer is: E. No error
The sentence is grammatically correct. The word “even if” introduces a condition that is contrary to fact. The doctor did put in his best efforts, but he could not succeed in saving the patient. The infinitive phrase “to save the patient” is the object
of the verb “could not succeed in.”The other options are incorrect because they suggest that there is a grammatical error in the sentence. Option A suggests that the word “even” should be followed by a comma. Option B suggests that the word “put” should be followed by an article. Option C suggests that the word “could” should be followed by an article. Option D suggests that the word “saving” should be followed by a comma.