Explanation: To answer this question, we need to understand the phases of project development and the associated costs.

The typical phases of project development are Analysis, Design, Implementation, Maintenance, and Documentation.

• Analysis: This phase involves identifying the problem, gathering requirements, and analyzing the feasibility of the project. This phase usually incurs moderate costs, as it involves a lot of research and data gathering.

• Design: This phase involves designing the system architecture, developing the user interface, and creating detailed specifications. This phase typically incurs moderate costs, as it involves a lot of planning and design work.

• Implementation: This phase involves coding, testing, and integrating the system components. This phase typically incurs high costs, as it involves a lot of coding and testing work.

• Maintenance: This phase involves ongoing support, bug fixing, and system updates. This phase typically incurs high costs, as it involves ongoing maintenance and support work.

• Documentation: This phase involves creating user manuals, system documentation, and training materials. This phase typically incurs low costs, as it involves documentation work.

Therefore, the correct answer is D) Maintenance. This phase typically costs the most, as it involves ongoing maintenance and support work.