Here was my approach, not sure if it's right:
The split I did was "that" vs "no that"
Sources of substances used for not only medicinal and cosmetic purposes but also as food preservatives and dietary supplements, aloe vera plants that are in the wild grow faster than they do when they are indoors, though they are a hardy houseplant.
A) Sources of substances used for not only medicinal and cosmetic purposes but also as food preservatives and dietary supplements, aloe vera plants
that are in the wild grow faster than they do when they are indoors, though they are a hardy houseplant.
The "that" restricts aloe vera plants to only those in the wild, so aloe vera plants that are in the wild are a hardy houseplant? How can a plant that is in the wild now be a houseplant now? Either the plant is in the wild or it's in the house. It can't be a plant that is in the wild and in the house.B) Sources of substances used not only for medicinal and cosmetic purposes but also as food preservatives and dietary supplements,
aloe vera plants grow faster in the wild than they do indoors, though they are a hardy houseplants.
C) As sources of substances used not only for medicinal and cosmetic purposes but also as food preservatives and dietary supplements, aloe vera plants
that are in the wild grow faster than they do when they are indoors, although they are a hardy houseplants.
Same as A explanation.
D) Although a hardy houseplant, aloe vera plants
that are in the wild grow faster than they do when indoors, and they are sources of substances not only used for medicinal and cosmetic purposes but also as food preservatives and dietary supplements.
Same as A, because the modifier "Although a hardy houseplant" modifies "aloe vera plants THAT are in the wild"E) Although they are hardy houseplants,
aloe vera plants in the wild grow faster than when indoors and are sources of substances used for not only medicinal and cosmetic purposes but also food preservatives and dietary supplements.
Now between B and E =>
E says "Although" which I generally of although as comparing a positive element to a related negative element or visa versa (comparing a negative element to a positive element). Here is says "Although they are hardy houseplants" (positive)... but sources used for medicinal/cosmetic purposes (positive). The although sounds weird here because it's two positive elements, so why are we using although?
So I thought the correct answer was B.