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.
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
TAT网址被河蟹了。。。那我粘过来好啦
看看原文:In the 1820s substantial anthracite coal fields opened in eastern Pennsylvania, and as canals and eventually railroads reached into the region, substantial supplies became available to the nation’s burgeoning mills, forges, factories, and railways.
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.
我认为换成when就错了,可以换成after。
只所以我认为there be 没有错,是因为当初在中学的时候学习句型之间的变换E的表达方法和A是完全可以相互变化的。尽管不能说句型的变化以后意思完全相同。这里E的表达方法也确实比A要好,但是比起你说when在E中也勉强可以算对,我认为A中的there be并不是关键的错误