以一个辅音字母结尾的重读闭音节动词，双写词尾辅音字母，再加 -ed，
如： stopped begged fretted dragged dropped planned dotted

以下动词加-ed或-ing要双写最后一个字母
1. regret (regretted, regretting) 后悔
2. control (controlled, controlling) 控制
3. admit (admitted, admitting) 承认
4. occur (occurred, occurring) 出现
5. prefer (preferred, preferring) 宁愿
6. refer (referred, referring) 提到
7. forget (forgetting ) 忘记
8. permit (permitted, permitting)允许
9. equip (equipped, equipping) 装备
注意：quarrel, signal, travel中的l可双写（英国英语）也可不双写（美国英语）