preposition ZAI (在) be followed by time, location, range, condition, and agent:
Time: 演唱會的門票會在今天上午十點鐘開始發售。
The tickets to the concerts will go on sale at ten o'clock this morning.
Location: 我本科是在杭州讀的。
I completed my undergraduate program at Hangzhou.
Range: 年齡在十八到二十五歲的市民，可以享受這項優惠政策。
The citizens aged eighteen to twenty-five are eligible to enjoy the benefits of this policy.
Condition: 在老師的細心教導下，他的成績有了顯著提高。
His grades improved significantly after receiving the meticulous training from his teacher.
Agent: 在我看來，這件事要交給警方處理。
The way I see it, we have to report this matter to the police.
