The correct answer is A. to build a model of the decision¬making problem.
A decision support system (DSS) is an interactive computer-based system that helps decision makers analyze data and make better decisions. DSSs are used in a variety of fields, including business, government, and healthcare.
The main purpose of a DSS is to help decision makers build a model of the decision-making problem. This model can be used to simulate different scenarios and to evaluate the impact of different decisions.
The other options are not correct because they are not the main purpose of a DSS. Option B is to design a database management system. A database management system is a software system that allows users to create, store, and manage data. Option C is to build an expert system. An expert system is a computer program that can make decisions like a human expert. Option D is to determine the key decisions in the problem area. This is a task that can be done by a DSS, but it is not the main purpose of a DSS.
In conclusion, the correct answer is A. to build a model of the decision¬making problem.