在
解説
介词“在”用于引出动作发生的地点或时间，常放在动词前作状语。
The preposition '在' is used to indicate the location or time where an action takes place, typically placed before the verb as an adverbial.
例文
哥哥在北京学中文。
My older brother studies Chinese in Beijing.
他在手机上看电影。
He watches movies on his phone.