GMATPill
Metallurgy, the process of refining metals from naturally mined ores,
as a method of the moulding of metals, it was well known as early as the medieval period, but until about several decades ago workers did not realize that bacteria take an active part in the process.
(A) as a method of the moulding of metals, it was well-known
(B) as a method of the moulding of metals well-known
(C) was a well-known method of metal moulding
(D) was a well-known method of moulding metal that was
(E) had been a method of metal moulding, well-known
Original Source: Practice Pill PlatformMetallurgy,
the process of refining metals from naturally mined ores,
as a method of the moulding of metals, it was well known as early as the medieval period, but until about several decades ago workers did not realize that bacteria take an active part in the process.
striked part is a modifier ..now if we read this sentence ....we can easily make out that there is no verb for the subject metallurgy.
hence this wrong.
basing this error ...we can easily eliminate option A and B.
OPTION E is wrong because of use of past perfect ..which is not required here..hence wrong.
now left with option C and D
(C) was a well-known method of metal moulding==>CORRECT
(D) was a well-known method of moulding metal
that was==>THAT WAS as early as the medieval period==>THIS DOESNT MAKES SENSE as pronoun THAT is refering to METAL.
hence C