Which activity is part of the design development phase that ensures the practicality of designs?

The design development phase is a crucial part of the architectural design process where ideas transition from concept to a more defined state. In this phase, practicality is emphasized to ensure that the designs are not only visually appealing but also feasible based on various constraints, including budget, materials, and manufacturing methods.

Creating sketches is an important activity that allows architects to visualize ideas and iterate on designs quickly. However, sketches alone don't address practical implications like cost and buildability.

Estimating project costs is essential in the design development phase, as it ensures that the proposed designs align with the client's budget and financial constraints. This step helps identify potential design modifications before committing to expensive construction processes.

Mockup creation is another critical component during this phase. It involves constructing physical or digital models of certain sections of the design, allowing stakeholders to assess scale, materials, and functionality in a tangible way. This hands-on approach helps reveal issues that may not be apparent in two-dimensional representations.

By including sketches, cost estimation, and mockup creation, the correct answer encapsulates the holistic approach required to ensure the practicality of designs throughout the design development phase. Each of these activities significantly contributes to refining the design and ensuring that it is both implementable and meets the project's goals.