急性上呼吸道感染
参考答案：急性上呼吸道感染 是指鼻腔、咽或喉部急性炎症的总称。常见病因为病毒，少数由细菌引起。
The _____ person in the street is a lot better than they were forty years ago.
[ ]
A. normal
B. average
C. regular
D. usual
当气缸分段处与放气口重合时实现（）是最方便的。
