The poster proclaims: "Let the new biological pesticide containing micro-organisms be your new best friend! Because it's used by 4 out of every 5 florists, you can be sure that this product will answer your pesticide needs."
Let's consider at least 2 points from our side to weaken the advertisement:
1.
Attack the evidence given: Can you surely tell if 4 out 5 florists are using this product then the product will be good? No, maybe 4 out of 5 florists are suffering from bug attacks who knows? And florists are yet to change the formula.
2. There might be another reason for this mass usage of biopesticide such as the company might have given it for free ( samples )
Which of the following, if true, most seriously undermines the advertisement's argument?
(A) Though an efficient pesticide on the East Coast, the new biological pesticide has yet to undergo satisfactory experimentation in other areas :
No, this doesn't prove why the advertisement will not succeed in the required area. (B) The company promoting the new biological pesticide sent free samples of it to all florists in the urban centres of the East Coast:
Yep, this is the reason why florists are using this product for the short term. The product may not be that effective but why miss the opportunity when the company wants to give it for free? However, we have a small problem here, i.e they have specified something called "Urban centre"!(C) Two years ago, most florists were using a chemical pesticide that was popular at the time while two years prior to that, another brand of chemical pesticide was considered the norm :
So what, who says the company is aiming for long term sales? An easy POE(D) The Nursery Newsweek, published at the time of the advertisement, called on florists to move from chemical pesticides to biological ones, elaborating on the latter's advantages :
This is more like a strengthener to our argument rather than a weakener.(E) Pesticides are needed more in nurseries than in florist shops, where plants and flowers are usually held for short periods of time :
hmmmm, a little difficult one to rule out and also a little ambiguous. Let's say nurseries use 100 tonnes of pesticides a month, but florists may still use 90 tonnes. So companies may be targeting a good chunk of sales here. And if florists are using this fertilizer, the nurseries might get attracted as well. So I will reject this choice.
Between B and E ,I will choose option B and move on.