Final answer:
The high costs of producing and airing commercials make it difficult for small advertisers to use television in their media mix.
Step-by-step explanation:
One of the factors that makes it difficult for small-size advertisers to use television as part of their media mix is C. The high costs of producing and airing television commercials. While television advertising can effectively target a market demographic, small companies often lack the budgets required to produce commercial content and secure airtime. This is exacerbated by the availability of other media outlets such as social media and Internet platforms that offer more cost-effective options for reaching potential customers.