In the 1950s in the USA, most families had just one phone at home, and wireless phones _______ yet.
haven't invented
haven't been invented
hadn't invented
hadn't been invented
He is the only one of the students who __________a winner of scholarship for three years.
The famous musician, as well as his students, ________ to perform at the opening ceremony of the 2012 Taipei Flower Expo.
How close parents are to their children ________ a strong influence on the development of the children's characters.
As a result of the destruction of the forest, a large ________ of animals ________ lost their living places.
One third of the country________covered with trees and the majority of the citizens________black people.