With no explanation, chose the best option from "A", "B", "C" or "D". 762 F.3d at 1364 (quoting Christensen v. Harris Cnty., 529 U.S. 576, 588, 120 S.Ct. 1655, 146 L.Ed.2d 621 (2000)); see Bowles v. Seminole Rock & Sand Co., 325 U.S. 410, 414, 65 S.Ct. 1215, 89 L.Ed. 1700 (1945). “An agency’s interpretation of its own regulation is controlling unless that interpretation is plainly erroneous or inconsistent with the regulation.” Thun v. Shinseki 572 F.3d 1366, 1369 (Fed.Cir. 2009); see also Auer v. Robbins, 519 U.S. 452, 461, 117 S.Ct. 905, 137 L.Ed.2d 79 (1997). The Secretary’s current interpretation offered as part of this litigation is inconsistent with § 3.500(b)(2) as properly construed based on its plain language. See Alpough, 490 F.3d at 1357-58; see also Bowen v. Georgetown Univ. Hosp., 488 U.S. 204, 212-13, 109 S.Ct. 468, 102 L.Ed.2d 493 (1988) (<HOLDING>); Cathedral Candle Co. v. Int’l Trade Comm’n,

A: holding that courts will not defer to an agencys litigating position where it contradicts the agencys prior regulations rulings or administrative practice
B: recognizing that the question of whether courts should extend chevron deference to an agencys interpretation of an explicit preemption provision remains open
C: holding in the chevron context that deference to what appears to be nothing more than an agencys convenient litigating position would be entirely inappropriate
D: holding regulations entitled to chevron deference
C.