We have had several visits ______the famous nature zoo.

The old man smiled when he saw how pretty__________up to be during the past few years.

I plan to take a boat trip to Hawaii next month. —That’s great! ____________.

The theory he sticks to ______ to be of no use in our studies.

We must make sure that public facilities(设施)in the newly-built building, like the restroom and the lift, are.