(2013·北京卷) --- Do you think Mom and Dad late? --- No, Swiss Air is usually on time.
Between the two lectures _____ a break, _______ the audience can buy ice cream.
Have the villagers already known ________ we’ll do is to rebuild the bridge?
—Did you forget about my birthday? —________. I should have booked a table at Michel’s restaurant for you.
It is known to all that ________ People’s Republic of China is ________ biggest developing country in the world.
No one has _____ been able to trace the author of the poem.