1.（），if he does not learn he knows nothing.选项：A.Man is ever so clever B.Be a man ever so clever C.No matter how clever be D.So clever a man ever is
2.The llama and the camel,though native to very different parts of the globe ,()of the same family.选项：A.are members B.but are members C.and are members D.they are members
3.Kunming is often cool in the summer ,but Shanghai ().A.is rarely B.scarcely is C.hardly is D.rarely is A和D选项有什么区别

1B
Be a man ever so clever = Whether a man a clever or not
这是一个倒装省略的特殊结构,作表示让步的状语

2A
这是一个though引导的让步状语从句,主句被分拆开来了.
B和C的错误:有了从属连词(though)引导状语从句,就不能再在主句中用并列连词,不论是意思上一致的but还是不一致的and.
D的错误:主语的重复

3D
完整的句子中状语的位置是:
频度副词(如:sometimes、often、rarely等)位于助动词或情态动词之后、行为动词之前。

但是如果句子是一个省略句，则频度副词要置于主语和助动词之间。

其他副词也有相应的规则，如时间状语和地点状语的先后排列等，这里就赘述了。