If the new airboat does what it is to be doing-----travel at high speeds undeterred by sandbars crocodile-infested mudflats, or marshy hippo haunts---it could revolutionize transport on the 2,900-mile-long Congo River. A. If the new airboat does what it is to be doing B. If the new airboat does what it is supposed to do C. If it does as the new airboat is supposed to do D. Doing what it is the new airboat is supposed to do E. Doing what the new airboat is to be doing
下划线是红色部分,答案是B。我对别的选项到是没有疑问,但是对于正确答案B有问题要请教大家。 关于虚拟语气一直不懂,B选项为什么不用虚拟呢?对现在的虚拟?因为文章后面it could revolutionize transport on the 2,900-mile-long Congo River,这个could 不也是虚拟语气的标志吗?那B这么对吗?为什么不是 if the new airboat did what it was supposed to do? 这个不是虚拟语气的正确的表达形式吗?请大家帮助我,太感谢大家了!!!