上课的时候，请注意黑板上的几个生词。

Shàngkè de shíhou, qǐng zhùyì hēibǎn shàng de jǐ gè shēngcí.

During class, please pay attention to the new words on the blackboard.

考试的时候要特别注意时间。

Kǎoshì de shíhou yào tèbié zhùyì shíjiān.

During exams you need to pay special attention to the time.