Marketing research is best defined as

a$)$ a framework for the day$-$to$-$day management and structuring of information gathered by marketers.

b$)$ an intuitive process for making decisions based on personal knowledge and experience to take advantage of market opportunities.

c$)$ the use of tools and methods to measure and interpret the effectiveness of a firm's marketing activities.

d$)$ the systematic design, collection, interpretation, and reporting of information to help marketers solve specific marketing problems or take advantage of market opportunities.

e$)$ the collecting of data from secondary sources and internal documents.