In the new curriculum, some courses are        , while others are optional for middle school students.

We’re expecting Jerry because he’s our _________ visitor who comes here for holiday every summer.

All the candidates present at the conference have contributed to the development of our country, so they are each recognized specialists in their _________fields.

I can’t go _____ because I have to go home at once. 

The businessman offered a(n) __________ price for one of her collections, giving her a pleasant surprise.