28-20: In the 1820’s, anthracite coalfields opened in eastern

Pennsylvania, and when canals and eventually railroads reached into

the region, there were substantial supplies of coal that was

exported to the nation’s growing mills, forges, factories, and

railways.

A: when canals and eventually railroads reached into the region,

there were substantial supplies of coal that was

B: once canals and eventually railroads reaching into the region,

there were substantial supplies of coal having been

C: with canals and eventually railroads reaching into the region,

there had been substantial supplies of coal

D: canals and eventually railroads reached into the region, with

substantial supplies of coal being

E: as canals and eventually railroads reached into the region,

substantial supplies of coal were

这道题我选E, NN们请指教。

支持E.

A: when canals and eventually railroads reached into the region, there were substantial supplies of coal that was罗嗦

B: once canals and eventually railroads reaching into the region, there were substantial supplies of coal having been罗嗦，并且having been错

C: with canals and eventually railroads reaching into the region, there had been substantial supplies of coal罗嗦，并且算上exported就出现了两个谓语动词

D: canals and eventually railroads reached into the region, with substantial supplies of coal being连句子主干都给颠倒了