小张近一段时间皮肤干燥，一到黄昏就看不清东西，体内可能缺乏（  ）

A．维生素A

B．维生素B

C．维生素C

D．维生素D

Without the friction between their feet and the ground, people would () be able to walk.

A. in no time

B. by all means

C. in no way

D. on any account