A certain experimental fungicide causes no harm to
garden plants, though only if it is diluted at least to
ten parts water to one part fungicide.Moreover, this
fungicide is known to be so effective against powdery
mildew that it has the capacity to eliminate it
completely from rose plants. Thus this fungicide, as
long as it is sufficiently diluted, provides a means of
eliminating powdery mildew from rose plants that
involves no risk of harming the plants.
Which one of the following is an assumption on
which the argument depends?
(A) There is not an alternative method, besides
application of this fungicide, for eliminating
powdery mildew from rose plants without
harming the plants.
(B) When the fungicide is sufficiently diluted, it
does not present any risk of harm to people,
animals, or beneficial insects.
(C) Powdery mildew is the only fungal infection
that affects rose plants.
(D) If a fungicide is to be effective against powdery
mildew on rose plants, it must eliminate the
powdery mildew completely.
(E) The effectiveness of the fungicide does not
depend on its being more concentrated than
one part in ten parts of water
I picked A but the ans is E- WHY??
Thank you so much @