Directions: In the following question, a sentence is given with certain words in bold. Choose the pair/s of such words which need to be interchanged so as to make the sentence grammatically correct and meaningful. 

Consider a (A) numerical real-world problem, like those of marketing or making (B) governing for a nation, where there are many (C) policies factors and most of them cannot be expressed as (D) complex time series data, as one would like to have for (E) building mathematical models.