He has an alert mind.
The alert listener will have noticed the error.
He is a man alert in problem.
Our guerrillas suddenly became alert as the dogs barked.
The rabbit seems to be very alert all its life.
S+be+～+ prep. -phrase
Be alert for any sign of change in the patient.
The student is alert in answering the question.
A monkey is very alert in its movements.
He is always alert to danger.
She was alert to seizing an opportunity.
So alert she was that not a single error in the report slipped her.
The voice of the caller alerted her.
Sirens alerted the cities long before the enemy bombers arrived.
They alert the public to the need for pollution control.
He had phoned the nearby villages, alerting them to the possibility of forest fires.
The guard was alerted by a man climbing towards him.
S+～+ n./pron. +that-clause
The boss alerted the guard that thief might come out at night.
The villagers alerted the traveller that wolves might come out in the night.
S+～+ n./pron. +to- v
The radio alerted coastal residents to prepare for the hurricane.
We will alert operating personnel to repair.
There are hurricane warning systems for alerting island residents.
A national police alert was in effect.
The hurricane alert is over.
The air-raid alert sounded at noon.
We'd just boarded the bus when the alert sounded.
If there is an alert, don't panic, just make your way to the exit.
The machine sounded the alert.
They received the alert at midnight.
It's the alert signal.
They were quiet during the alert.
We should not run about aimlessly during an alert.
The whole country is in a state of alert.
Security forces are on a high state of alert because of the President's visit.
Sirens brought the whole street to the alert .