The traffic rule says young children under the age of five and _______ less than 25 kilograms must be in a child safety seat. 

That light rail transit line(轻轨)，started in July 2009 and _________in 2012, will be China’s longest light rail transmit line in history.

If ____unsolved, the problem of food safety may lead to more serious results.

Professor Smith, along with his assistants, ________ on the project day and night to meet the deadline.

When a person is absent-minded, he is likely to miss key information ______ on to them.