With no explanation, chose the best option from "A", "B", "C" or "D". to an element of a claim or defense as to which State law supplies the rule of decision, the privilege of a witness, person, government, State or political subdivision thereof shall be determined in accordance with state law.” Fed. Evid. Rule 501. The state of Arizona recognizes the physician-patient privilege. Duquette v. Superior Court, 161 Ariz. 269, 778 P.2d 634 (Ariz.App.1989). III. Discussion By its motion in limine, Defendant seeks to interview Plaintiffs treating physician ex parte in advance of the treating physician’s deposition. The government argues that courts have held that federal common law permits ex parte contact with treating physicians, and it asks this Court to follow the reasoning of those courts. See Sipes v. United States, 111 F.R.D. 59, 61 (S.D.Cal.1986) (<HOLDING>); Filz v. Mayo Foundation, 136 F.R.D. 165

A: holding that a request for admission is a tool of discovery subject to discovery cutoff dates
B: holding that ex parte young exception to states sovereign immunity applies only where violation of federal law is ongoing not where federal law was violated only in the past
C: holding that federal common law allows ex parte interviews as discovery tool and controls even when state law supplies the rule of decision
D: holding that minnesota law prohibiting ex parte interviews was not integral to its privilege law but was merely procedural rule and therefore not controlling in diversity action and the federal rules allow ex parte interviews as method of informal discovery
C.