Your letter will get ___ attention; they know you're expecting the answer.

A．careful

B．common

C．instant

D．general

嗜铬细胞瘤的特征性临床表现是（）

A.持续性高血压

B.阵发性高血压

C.持续性低血压

D.阵发性低血压

E.高血压与低血压交替出现