单项选择题
Vingo was released from prison ______ the successful efforts of his friends to prove his innocence.
单项选择题 The company is starting a new advertising campaign to ______ new customers to its stores.
单项选择题 Over the past decades, sea ice ______ in the Arctic (北极) as a result of global warming.
单项选择题 ______ twice, the postman refused to deliver our letters unless we chained our dog.
