—Look! The man at the gate              be our headmaster. He is always standing there every morning.

—No, it              be him, He is having a meeting in the office now. [ ]

A. must, can't

B. must, mustn't

C. can, can't

患者女性，36岁，近年来，感觉双下肢沉重酸胀、易疲乏，休息后症状减轻。就诊时可见双下肢内侧静脉明显隆起，蜿蜒成团，Trendelenburg试验阳性。

可能的诊断是

A．下肢静脉曲张
B．动静脉瘘
C．深静脉血栓形成
D．血栓闭塞性脉管炎
E．动脉硬化闭塞