Which of the following methods is considered most appropriate for addressing the marketing needs of a product at the current stage in its lifecycle?

The question seems subjective and hence basing on the kind of product and the market it has to cater,each method warrants its own implementation at different stages of the products' lifecycle and thus option B should suffice.

As a and  c and d far from the correct answer .. I think it is B

I am not a marketing expert but I'd go with B) but also considering A)

b) Objective and task

is the answer

I am not quite clear with what stage you are asking about. Each fo these apply to different stages at different points in time. 

Still. the best way to address market needs one that can apply to every stage is indeed (and I agree with Mr. Vinod), (C) objectives and tasks that are inline with the mission statement, value proposition behind the product and the brand.

b) Objective and task............... . . . .