描述成人喉 * * 状瘤的特点正确的为（）。
A.与生殖器尖锐湿疣有关
B.常为多发性
C.容易发生喉阻塞
D.有恶变可能
E.不易复发
参考答案：B
下列符合纯粹公共品的特性的是（）。
A.谁付款、谁受益
B.边际成本为零
C.边际成本大于边际效益
D.消费的竞争性
9. _____frightened us ____the electricity was suddenly cut off, which threw all of us into the dark.
A． It was; that
B．What was; most was that
C． It ; most what
D． What; most was that
