当你在学校学习时，你必须努力学习，不要放弃。

When you learn your lessons in school, you must work hard and not give up.

youdao

首先，你必须努力学习功课，并在考试前做好充分的准备。没有充分的准备，很难正确回答所有的问题。

To begin with, you must work hard at your lessons and be fully prepared before the exam. Without sufficient preparation, you can hardly expect to answer all the questions correctly.

youdao

你必须努力学习以免你考不及格。

Youmust study hard lest you (should) fail the test.

youdao