________ twice a year, whether it is a car or a bus or a truck, is the rule that every driver must obey in this city.
. The driver _________, according to the newspaper, to have been killed in the traffic accident.
. The custom of giving gifts at Christmas can be traced back to the Wise Men _________gifts to the baby Jesus.
. _________at the very beginning, the financial crisis was getting worse and worse in America.
. The higher the oil price is, ___________to the global economy.
. I made a call to my parents yesterday. To my disappointment, _________of them answered it.