These new types of energy from the sun, wind and water cost very little and will never ________.

The teacher，with 6 girls and 8 boys of her class，_____ visiting a museum when the earthquake struck.

had finished supper and _____ have a bath when the power was cut off. [ ]

The books on the left shelf ______ quite interesting. You could read them to your kid before bedtime.

Last Sunday, we visited the factory _____ my father ever worked for four years.