Though glass is the conventional way of providing cheap

[helloriteshranjan]

source: winningprep

Though glass is the conventional way of providing cheap, stable, and durable protection for motorists, but it is heavy, difficult to mould and potentially dangerous.

A- conventional way of providing cheap, stable, and durable protection for motorists, but it is heavy, difficult to mould and potentially dangerous.
B- conventional way of providing cheap, stable, and durable protection for motorists, it is also heavy, difficult to mould and potentially dangerous.
C- conventional way of providing cheap, stable, and durable protection for motorists, it is also heavy difficult to mould and is potentially dangerous.
D- conventional way of providing cheap, stable, and durable protection to motorists, it is also heavy, difficult to mould and potentially dangerous.
E- conventional way of providing a cheap, stable, and durable protection for motorists, it is also heavier, difficult to mould and potentially dangerous.

OA- B

my choice was D. what could explain the right answer.

thanks

[RonPurewal]

source: winningprep

Though glass is the conventional way of providing cheap, stable, and durable protection for motorists, but it is heavy, difficult to mould and potentially dangerous.

A- conventional way of providing cheap, stable, and durable protection for motorists, but it is heavy, difficult to mould and potentially dangerous.
B- conventional way of providing cheap, stable, and durable protection for motorists, it is also heavy, difficult to mould and potentially dangerous.
C- conventional way of providing cheap, stable, and durable protection for motorists, it is also heavy difficult to mould and is potentially dangerous.
D- conventional way of providing cheap, stable, and durable protection to motorists, it is also heavy, difficult to mould and potentially dangerous.
E- conventional way of providing a cheap, stable, and durable protection for motorists, it is also heavier, difficult to mould and potentially dangerous.

OA- B

my choice was D. what could explain the right answer.

thanks

first of all, this is NOT the punctuation convention used by the gmat. if the gmat uses a series of three or more items, connected by "and", then there WILL be a comma after the penultimate (next-to-last) item in the list.
so, there should be a comma after "mold". (also note that "mould" is a british spelling and so would not appear on the test)

the only difference between (b) and (d) is the idiom "protection to" / "protection for", so it's clear that this idiom is the deciding issue.
if you are doing something to protect person X, then that is protection FOR person X.
there's no such idiom as "protection to". (you could parse the incorrect answer as providing protection to motorists - i.e., the "to" is paired with "providing", not with "protection" - but this gives an incorrect/nonsensical meaning.)

[pawan_chitturu]

I narrowed it down to "B" and "A".

Can somebody please explain, why the usage of "but" is incorrect in option "A"?

[RonPurewal]

I narrowed it down to "B" and "A".

Can somebody please explain, why the usage of "but" is incorrect in option "A"?

stick that choice back into the original sentence and it may be more obvious where the problem is: you've got two conjunctions, "though" and "but", each of which is trying to perform the same job (i.e., indicate contrast).

i.e., you can't say
Though CLAUSE1, but CLAUSE2.

either of these would be an acceptable alternative:
CLAUSE1, but CLAUSE2.
Though CLAUSE1, CLAUSE2.

[pawan_chitturu]

Thanks for the explanation Ron