Having checked the doors were closed,andall the lights were off,the boy opened the door to his bedroom.
Only when I left my parents for Italy ___ how much I loved them.
It was not until 1920 ___ regular radio broadcasts began.
The reason _____ he explained is ___ she was ill.
_______, the disease diphtheria would produce a powerful poison that would kill the paient.
He ___ in Nanjing where he ____ by his aunt.