What Is the Key Challenge for Marketers

What is the key challenge for marketers?

A) The key challenge for marketers is to monitor competitors and match them in terms of their product, place, price and promotion
B) The key challenge for marketers is to develop a competitive advantage through marketing mix decisions, which are cost effective and maximise the company's profits
C) The key challenge for marketers is to continuously develop new, successful products as older products gradually decline in popularity
D) The key challenge for marketers is to monitor and understand customer needs and develop a competitive advantage through marketing mix decisions