甲方因急需柴油，与乙厂签订了一份买卖合同。双方商定，乙厂在1个月内筹集0号或10号柴油10吨供给甲方，每吨单价为1200元；合同生效后，甲方按合同约定支付了2000元定金。乙厂也在合同生效后第25天，依约定向某厂发运了0号柴油 10吨。因当时气温下降，0号柴油无法投入使用。故甲方要求乙厂改供10号柴油，或者退货。乙厂认为其所供0号柴油符合国家质量标准和合同规定，既不应换货，也无货可换；同时要求甲方依约支付贷款，不能退货。

本案合同所生之债应为：

A．简单之债，因为乙厂只向甲方发运了0号柴油10吨

B．简单之债，因为债权人甲方有选择权

C．选择之债，因为当事人约定了两种柴油种类

D．选择之债，因为债务人可以选择0号或10号柴油供给甲方

新概念。   

   I have just    1   a letter from my brother, Tim. He is in Australia. He has been there for six    2   . Tim is an    3   . He is working for a big    4   and he has already visited a great number of    5   places in

Australia. He has just    6   an Australian can and has      7   to Alice Springs, a small town in the    8   of

Australia. He will soon visit Darwin. From there, he will    9   to Perth. My brother has never been    10  

before, so he is finding this trip very exciting.