关于咯血与呕血的鉴别，下列哪项是错误的（）。

A.咯血不可能出现黑便，呕血一定出现黑便

B.咯血为鲜红色，呕血多为暗红色

C.呕血见于消化道疾病

D.咯血属碱性，呕血属酸性

E.咯血中混有痰、泡沫，呕血混有食物残渣、胃液

Tina was hesitation about the job offer as she did not know _______ the company was an established one.

A．whether

B．what

C．until

D．although