We must consider appropriate measures for this problem.

In this experiment, it is necessary to let the sample stand overnight.

This yogurt is left to stand for 24 hours to ferment.

Prepositions are an important part of grammar.

I placed the materials before the important meeting.

She is learning how to use prepositions in Chinese.

In Chinese grammar, separable verbs play a very important role.

His speech skillfully used interjections, captivating the audience.

It's difficult to make sentences using interrogatives.

It's difficult to make sentences using infinitives.