Official ExplanationThe question asks for something that supports a view, making this a Strengthen question. However, the view being strengthened is in the question stem itself: that Hitek Appliances will not increase sales. The gist of the stimulus is that more people are buying microwaves, so Hitek Appliances plans to make more microwaves and continue its present advertising campaign.
Remember that the conclusion to be strengthened is in the question stem: Hitek Appliances will not increase sales. It might seem unlikely, but note that the evidence is about microwave sales in general -- not just Hitek sales. To claim Hitek will not increase sales, it must be assumed that Hitek is not part of the general trend. To strengthen this view, the correct answer will validate the assumption and show why they won't get more sales.
(C) supports the assumption and is correct. This suggests that Hitek is not benefiting from the widespread increase in microwave sales. So, simply making more microwaves will not ensure that they will sell more microwaves.
(A) is a 180, at worst. If inventory is decreasing, that suggests Hitek is selling more and is thus part of the growing trend. That makes it likely they will increase sales.
(B) is a 180. If people think the product is high quality, that suggests Hitek could increase sales.
(D) is a 180. This suggests Hitek is, indeed, part of the current trend and is thus likely to see a continued increase in sales.
(E) may seem tempting, but read carefully. It states that Hitek's share of the market — not the total number of microwaves sold — has declined, and that they are selling almost all of the units they produce. Market share could drop merely due to higher sales by other companies. However, if Hitek can retain a 95% sales rate, then increasing production could still increase sales.
TAKEAWAY: Read the question stem carefully and completely. It may ask for something that goes against the stimulus.