Drivers must be on the alert for traffic signals.
They want to be on the alert for similar buying opportunities.
When you back out of your driveway or leave your garage, be on the alert for children who are walking or bicycling to school.
Considering the fact that the patient's heart,lungs,kidneys and Brain functions have remained poor, one should be on the alert for an accident that might recur at any time.
Police warned the public to be on the alert for suspected terrorists.
We have been worried about the possibility of war and have had to be on the alert every year.
Yellow - be on the alert.
The police of Marseilles will be on the alert by land, whilst the governor pursues me by sea.
Every country that advocates peace must be on the alert.
Currently, first, the BRICs should be on the alert that hostile powers in developed countries may make mischief between them under the cover of ideology and history-made problems;
Police are warning the public to be on the alert for suspicious packages.
We are therefore campaigning for authors, researchers and editors to be on the alert for plagiarism and to work against cultural misunderstandings.
