Walking alone in the dark，the boy whistled to ________ his courage.

You must read the _______ with great care to see if the drug contains PPA before it is taken.

Many restaurant menus include the origins of a dish, _______ it is prepared, what the main ingredients are, and which farms the ingredients come from.

Nokia has    a family    of low-cost mobile phones based on Google's Android operating system.

The driver should be punished! He shouldn’t _______________ running red lights.

(2013·大连二模)We each ________ strong points, but each of us on the other hand ________ weak points.

—What does PM 2.5 mean?
—It's a professional ________ indicating the condition of air  pollution.

(2013·江西景德镇市一模)This online game has been intended to improve children's ________.

(2013·陕西宝鸡模拟)After Queen Elizabeth officially opened the 2012 Summer Olympics, London became the first city ________ three Olympic Games in history.

(2013·四川高考)________ which university to attend, the girl asked her teacher for advice.