向ＮＮ们求救

never3738

想请问大家，关于主谓省略，是不是一定要同时省略，不能单独省略主语，　或仅仅省略一个谓语？　

例１：

GWD-25-37

Though the law will require emissions testing of all diesel vehicles, from
                tractor trailers to execursion buses, it will have no effect on sport utility
                vehicles, almost all of which are gasoline powered and therefore not subject to
                    emissions-control standards as stringent as those fordiesel-powered vehicles.

almost all of which(主语) + are（谓语） ............　and　（同时省略主谓）not subject to．．．．

GWD-26-12

The most vexing problem faced by researchers exploring wind-powered
                generation of electricity is   how to achieve a constant flow of power
                    from an unpredictable natural source, a flow that meets demand but does not overload
                    electrical grids with sudden
                voltage increases

a flow (主语)  meets(谓语) 　but（只省略主语）does not (谓语)...........

为什么例１：同时省略；例２：只省略主语呢？

谢谢大大们。

ricee

问题有些奇怪啊，第一句省略了与前面相同的are,第二句否定形式你要他怎么省助动词啊，省了你意思怎么表达呢