这个题搞不明白, 请NN指教

18.   

Over the course of the eighteenth century, the average
output of ironwork tripled as a result of several improvements in blowing
machinery and because coal replaced charcoal as the fuel used in the smelting
of iron ore.

A.      Over the course of the eighteenth
century, the average output of ironwork tripled as a result of several
improvements in blowing machinery and because coal replaced charcoal as the
fuel used in the smelting of iron ore.

B.       Over the course of the eighteenth
century a tripling in the average output of ironwork was due to the replacement
of charcoal by coal for the fuel used in the smelting of iron ore, in addition
to several improvements in blowing machinery.

C.      With charcoal’s being replaced by
coal as the fuel used in the smelting of iron ore and several improvements in
blowing machinery, the average output of ironwork tripled over the eighteenth
century.

D.      The replacement of charcoal with
coal for the fuel used in the smelting of iron ore and several improvements in
blowing machinery, the average output of ironwork tripled over the eighteenth
century.

E.       Charcoal being replaced by coal as
the fuel used in the smelting of iron ore, and several improvements in blowing
machinery, which tripled the average output of ironwork over the course of the
eighteenth century.

The answer key  is  A, but   I feel C is better..?请NN指教

BY说sb's being一定错……

而且C的句意有所改变