PT 24 Sec 3 Q11

Jonathan W.

Hi all,

I hope someone may be able to clue me in as to what I'm doing wrong with this problem. This is a MBT.

Special kinds of cotton that grow fibers of green or brown have been around since the 1930s but only recently became commercially feasible when a long-fibered variety that can be spun by machine was finally bred. Since the cotton need not be dyed, processing plants avoid the expense of dyeing and the ecological hazards of getting rid of leftover dye and by-products.

So I understood how to diagram the stimulus. "Spun by machine --> commercially viable"

When I looked at answer choice (B): Green and brown cottons that can be spun only by hand are not commercially viable" I diagrammed it as "Spun by hand --> /commercially viable". In order to get to answer choice (B), you would need to negate the sufficient and necessary which gives "/Spun by machine --> /commercially viable" which is an invalid argument form (mistake in negation).

What am I doing wrong? I am having a hard time seeing how answer choice (B) can be diagrammed as "/commercially viable -->spun by hand" Thanks!

nye8870

Hey there @"Jonathan W."
“Special kinds of cotton that grow fibers of green or brown have been around since the 1930s --but only recently became (commercially feasible) when a long-fibered variety that (can be spun by machine) was finally bred.”
Reworded:
Until green and brown fibers were bred as long-fibers which could be spun by machine, green and brown fibers were not commercially feasible.
Negate sufficient… /spun by machine --> /commercially feasible
Ac(B) refers to green and brown cottons spun only “by hand.” What do you call green and brown cottons that can only be spun only by hand? “/spun by machine”
Not spun by machine leads to not commercially feasible ac(B) .