When the statement was made, the plane ______.

29．__________ when you are on the bus or bike．

Jane said she would rather __________when she was working on the project.

—When can I call on you, afternoon or evening?
—________. I’ll be at home all the time.

Only when we hurried to the airport__________the flight was cancelled.

In ______, the only element that can be deleted or removed is the one that was inserted most recently.

（ ）Some students prefer yellow rulers or erasers when they study for exams because yellow is the color of __________.

Virginius would feel more or less guilty when he______.

Believe it or not, when first (introduce) ____ to Europe, tomato was thought to be poisonous.

Project ______is an uncertain event or condition that，if it occurs，has a positive or a negative effect on at least one project objective，such as time，cost，scope，or quality．

The British Empire was replaced by the British Commonwealth or the Commonwealth of Nations in_____.

He served the army in ______ when he was in_______.