1. If you need extra ammo fly over your base and collect it. 如果你需要额外的弹药飞越你的基地，并收集它。
2. An extra elevator or second bank of elevators must be added. 额外的电梯或第二银行的电梯必须补充的。
3. We have a teacher at my school who gives us extra lessons sometimes. 我们学校里有名老师有时给我们上一些额外的课程。
英英解释
n.
1. a minor actor in crowd scenes
2. an additional edition of a newspaper (usually to report a crisis)
3. something additional of the same kind adj.
1. more than is needed, desired, or required
2. added to a regular schedule
3. further or added adv.
1. unusually or exceptionally
