Once in the classroom, I raised my hand and stood up to speak to our teacher.

最终在教室里，我举手示意并站起来对老师说出了我们的想法。

youdao

If they're not sure about something they hear, it can turn into a more formal lesson once back in the classroom.

如果他们对听到的东西不是很确定，就可以把这些东西以更正式的形式在课堂上展开。

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Once inside the virtual classroom, they have access to a chat feature, an interactive white board and a video window where they can see and hear the tutor in live video and audio.

一旦进入虚拟课程，他们就可以进入聊天框，一个有互动功能的白板还有一个视频窗口，通过这个视频窗口他们可以看到教师的现场授课。

youdao

He volunteers in Neva's classroom once or twice a month and is one of the few fathers who does so.

WSJ: Being a Murphy Brown Working Mom in a June Cleaver Stay-at-Home World

Once, he remembered, a boy in the room next door was thrown against the classroom wall, and he watched the blackboard on his side of the wall come off its hinges and fall to the wooden floor.

NEWYORKER: Teaching