______ his timely help, Kate overcame the hardship at last.                                                                                                                                                                                                                                                                                                                                                                                                                         

A．Now that

B．Thanks to

C．Since

D．Because

利率期权合约通常以（）作为标的物。

A．政府短、中、长期债券

B．大面额可转让存单

C．公司债券

D．欧洲美元债券