I think it should be B.
Premises:1) Leading dailies have received several complaint about an advertisement for Sucrocorp's cheese.
2) 90% of the complaints have accused it of carrying racist undertones
3) Sucrocorp's market share > 20%
Conclusion:At least twenty per cent of consumers do not find the advertisement controversial.
How to arrive at conclusion:If out of 100, more than 20 people still purchase Suncrocorp's cheese => They dont have any problem with the ADs.Pre-thinking Assumptions:1)For the above link to be true, we should know for sure that
those 20 people have actually seen the AD. The conclusion breaks if we negate this.
2)The advertisements do impact the sale of a product
POE:A. Dislike of an advertisement has no impact on the likelihood that a consumer will purchase the product.
Opposite of this could have been a contender. (pre-thought assumption 2 above)
B. Sucrocorp’s consumers are aware of its advertisements.Bingo! If they are not aware of the ADs, the conclusion breaks.
C. The eighty per cent of consumers who do not buy Sucrocorp cheese consider the advertisement objectionable.
Just because the argument talks about %, please dont trick me with choices involving %

issue 1: The argument says that the market share is
at least 20, it can even be 100%. There wont be any people who do not buy this cheese.
Issue 2: The people who do not buy this cheese might not be buying it even before the ADs were published. (Causal error)
D. Most consumers in the dairy market prefer certain types of cheese to others.
This is irrelevant. We are not concerned about the 'preference' of customers.
E. Most of the complaints against the advertisement were by people who have themselves been the victims of racist attacks.
Irrelevant again.
Hence B.