扫描二维码，直接登录
题库 / Prep2007E1-SC-113
Thunderclouds form when warm, moist air rises into cooler air above, because either the ground is warmer than usually or because the interaction of two air masses, one warm and one cold, forces warm air to rise.
because either the ground is warmer than usually or because
because either the ground is warmer than usual or because of
because of either the ground being warmer than usual or because
either because of the ground's being warmer than usually or because of
either because the ground is warmer than usual or because
还没有题目讲解（毕出老师会陆续发布对官方考题的解读，请保持关注）。
md把句子都完整啊giegie
登录 或 注册 后可以参加讨论