根据组成字符的各比特在信道上是否同时传输这一特点，可将数据传输分为（）
A.串行传输
B.同步传输
C.并行传输
D.异步传输
参考答案：A, C
. __________ in Hangzhou station for two hours, the old man eventually caught the last train to go back to his home in Huangyan.
A．Waiting
B．To wait
C．Having waited
D．To have waited
下列搭配容易造成腹泻的是？（）
A.花生+生蟹
B.李子+鸡蛋
C.菠萝+鸡蛋
D.芹菜+肉
