An app builder at Northern Trail Outfitters created a sandbox template for Accounts, Projects, and...

A Partial Copy Sandbox is designed for testing and development with a subset of production data based on a sandbox template. Since the question mentions that a sandbox template was created for certain objects (Accounts, Projects, Project Milestones), the environment must support template-based sampling, which only Partial Copy and Full sandboxes do.

Why B (Partial Copy) is correct:Exact Extract:“A Partial Copy sandbox includes your organization’s metadata and a sample of your production data as defined by a sandbox template. Use it for quality assurance tasks, integration testing, and user training.” — Salesforce Help | Sandbox Types and TemplatesDeveloper and Developer Pro sandboxes do not support sandbox templates.

Why B (Partial Copy) is correct:Exact Extract:“A Partial Copy sandbox includes your organization’s metadata and a sample of your production data as defined by a sandbox template. Use it for quality assurance tasks, integration testing, and user training.” — Salesforce Help | Sandbox Types and TemplatesDeveloper and Developer Pro sandboxes do not support sandbox templates.

Why not A or C:Developer and Developer Pro contain metadata only — no data templates or sample data.

Why not D:Scratch Orgs are for source-driven development and are not created from sandbox templates.