_____ twice a year, whether it is a car or a bus, is a rule that every driver must obey in this city.
He was severely injured in the war and his __________ prevented him from holding any job.
_______ with a difficult situation, Arnold decided to ask his boss for advice.
Halfway up the mountain we stopped to ______________.
The doctor insisted that only in this ______ could the patient survive in the operation.
He hurried to the station only _______ that the train had left.