27.If you ________ to something different, for example to a different system, task, or subject of conversation, you change to it from what you were doing or saying before.
The system has been designed to give students quick and easy to the digital resources of the library.
Form their ________ on the top of the TV Tower, visitors can have a better view of the city.
Children need friendstheir own age to play with.
The ____________ shoes were covered with mud, so I asked them to take them off before they got into __________ car.
In our class, when the bell rang and the teacher closed his book, it was a ______ for everyone to stand up.