Sentence Correction

First my due apologies for not posting the entire stuff....

In commercial garment construction, one advantage of serging over single needle sewing is that the seam allowance is overcast as the seam is sewn instead of with a separate process requireing deeper seam allowance.

Kalpan says it should be rather than in


how can the construction be parallel
seam allowance is overast as x rather than in separate process



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Each of the factory owners that felt that pollution.....

kalpan says that is only used for things...

but manhattan says that can be both used for things and people.....

???



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grand canyon have typically seen layers of sediment in the gaping canyon, whose different colors are amazing.


kaplan says whose can refer to both layers and canyon...

but is the rule says whose, which, who... directly refer to the immediate precedent noun..

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alterations in mood, which xyz

now which refers to mood or alterations in mood.... ??


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The network determined that seventeen commercials should be shown during the half hour sitcom...

now i think we have to use subjunctive mood ???

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Appreciate your help!