题干
---What a long queue!
--- Yeah．We ________________ up in the past few hours for tickets back home．
--- Yeah．We ________________ up in the past few hours for tickets back home．
A：queued
B：have queued
C：are queuing
D：have been queuing
答案(点此获取答案解析）
D
甲醇——空气电池工作时的示意图。甲醇在催化剂作用下提供质子（H+）和电子，电子经外电路、质子经内电路到达另一极与氧气反应。下列说法中正确的是
