Referring to the Information Given, Who Retains the Burden of Proof

Referring to the information given, who retains the burden of proof if the doctrine of res ipsa loquitur does not apply? Assume that at a medical malpractice trial alleging postoperative infection exactly 50% of the evidence favors the plaintiff and 50% of the evidence favors the defendant physician and hospital. Among the defendant's evidence is some indication that the patient did not comply with postoperative care instructions, including taking antibiotics to fight infection.

A) Defendant
B) Plaintiff
C) Both a and b
D) Neither a nor b