and must serve to connect PARALLEL FORMS.Mechmeera wrote:I find option A still weird as it uses both because and as a result of in a sentence and that too in parallel parts of it.[/color]
Parallel forms serve the SAME FUNCTION.
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.
Here, each blue portion is an ADVERB serving to modify tripled, expressing WHY the average output TRIPLED.
Since the two blue portions serve the same function, they are considered parallel.
