單項選擇題患者,男,60歲。形寒便溏,完谷不化,夜尿頻多清長,下肢不溫,舌質(zhì)淡白,脈沉細(xì)。其舌苔應(yīng)是()

A.透明苔
B.白干苔
C.黃苔
D.黃膩苔
E.灰苔