He reads newspapers every day to keep himself _______ about what’s going on in the world

___ we know some basic knowledgeconcerning AIDS, we can protect ourselves from being infected.

The researchers who study jokes want to know peoplefrom different nations and cultures find funny.

I don’t know __________ or not the work will be completed on time .

The sweet smell of the flowers in the garden comes in _______ the open window, making us feel in good mood(心情).