Direct marketing is an effective tool for:

Direct marketing will be effective for both. 

Direct marketing allows you to generate a response from target customers. As a result, small businesses can focus their limited marketing resources where they are most likely to get results. A direct marketing campaing with a clear call to action can help you boost your sales to exisitng customers, increase customer loyality, recapture old customers and generate new business. 

Importanly, direct marketing can be evaluated and measured precisely. One can analysis results to see which target group was most responsive and can also test marketing strategy with sample groups before it being rolled out.

Wheather you are targeting business (B2B0 or customsers (B2C0, direct marketing can deliver results.

Direct marketing its a tool that have high ability to target a particular customer and it can be used for B2C and B2B .

DIRECT MARKETING IS method by which company reaches at door step of customer , directly through its agent.

OPTION "A"

For me its A, but its more like hitting two birds with one stone.

Well it depends on the nature of business.It all depends on the industry type and your product. If FMCG then A , If engnineering product then both options , etc.

Answer is (A)  

Answer is A whether you are targeting business.