Question

2．I would like to take this opportunity to thank my leader，without whose support/and without his supportour program
could not have been completed so smoothly．（support）
我想借此机会感谢我的领导，没有他的支持，我们的计划不可能这么顺利地完成．

Answer 1

分析 I would like to take this opportunity to thank my leader，without whose support/and without his support our program could not have been completed so smoothly．

解答 本句主句是表达自己的感激之情，用一般现在时，从句表示对过去事实的虚拟，所以用虚拟语气．
本句可以用一个定语从句without whose support our program could not have been completed so smoothly来修饰先行词my leader，也可以加上连词and构成一个并列句．
take this opportunity to do sth利用这个机会做某事；could not have done sth意为"本来不可能完成某事"．

点评 另外，but for，otherwise等均可引导含蓄虚拟条件句．如：
But for your help we couldn't have succeeded in the experiment．如果没有你的帮助，我们的实验是不会成功的．（=If it hadn't been for your help，we…）
I'm really very busy，otherwise I would certainly go there with you．我真的是太忙了，不然我就会同你一道去了．（otherwise=if I were not so busy）