关于呕血与便血的概念，下列叙述错误的是（）

A.呕血是指由上消化道疾病所致的消化道出血，血液经口腔呕出

B.由鼻腔、口腔、咽喉部出血吞咽后再呕出，也称呕血

C.消化道少量出血，隐血试验可为阳性

D.便血的病因可以为上消化道疾病，也可以为下消化道疾病

E.便血的颜色可呈鲜红色、暗红色或黑色

Letter A
Dear Rose,
I like your programmes very much. I’m now writing to ask you something about American social customs. My American friends want me to join them in their dinner party. I am very happy and have decided to go, but I’m a little worried about it, too. The social customs in my country are very different from here, so I’m afraid of making mistakes.
Should I bring a present, such as sweets or flowers Should I arrive on time or a little late At the dinner table, how can I know which fork or knife to use How can I let the family know that I’m thankful for their kindness
Wang Lin
Letter B
Dear Wang Lin,
It’s a good idea to bring a small present when you go to a dinner party. Flowers are always nice, or you may bring a bottle of wine if you know that your friends drink it.
You should arrive on time or five to ten minutes late. Don’t get there early. If you’re going to be more than fifteen minutes late, you should call and tell them.
Try. to be free at the dinner table. If you don’t know about choosing the right fork or knife, just watch the other people, and follow them. If you still have no idea of what to do, ask the person next to you.
If you like the food, say so. Of course, you’ll thank them for the meal and for their kindness. It’s also a good idea to send a thank you card the day after.
Rose

Which of the following is NOT proper for joining in a dinner party

A. Get there 15 minutes earlier.
B. Make yourself at home.
C. Follow others to use forks and knives.
D. Thank your friends for the meal.