The sound of the birds __________happy memories of my childhood holidays.
---Alice, why didn’t you come yesterday?--- I______, but I had an unexpected visitor.
His parents are very concerned about his son at school because he _______moving in his seat.
--- _____ the population of China? --- About 1.3 billion.
We look forward to the day when motorcars will be replaced by some less dangerous ____ of transport.
Mother _________father to give up smoking, but she failed.