【单选题】我国《合同法》规定,如果当事人约定由第三人向债权人履行债务,第三人不履行债务或者履行债务不符合约定的,( )应当向债权人承担违约责任。
【单选题】根据系统论,学生是教育系统的构成要素,其学习必然受整个教育系统的制约,是一种
【单选题】若以 x 轴为键轴,下列何种轨道能与 p y 轨道最大重叠 ?
【单选题】Consumers say they are_ about using their credit cards over the Internet because they are afraid of Internet fraud and identity theft.
【单选题】Consumers say they are_ about using their credit cards over the Internet because they are afraid of Internet fraud and identity theft.
【单选题】Consumers say they are ______ about using their credit cards over the Internet because they are afraid of Internet fraud and identity theft.