The mother didn't know who ________ for the broken glass as it happened.

  – Let’s go skating, shall we?--That’s not a good idea; the ice is too thin _____ your weight.

Three years ago in Beijing, my best friend, David, was hit by a car while riding a bike, _______ a terrible brain injury.

—What are you going to do this afternoon？  —I'm thinking of _____ to visit my aunt．

Television lets us see history in the making. We can watch sports, political debates, trials and even wars ________．