On 5 December 2013, China Central Bank prohibited financial institutions from handling Bitcoin transactions, _____ to regulate the virtual currency.
Winter is the time of the yearthe days are short and nights are long.
--- What ______ when I phoned you? --- I ______ my work, and I was about to go out.
It was the first time ________ I ________ face to face with a thunder storm.
We were having a meeting _________ suddenly someone knocked at the door.
The old woman has _______________ too many hardships in the past 10 years.