Step 1: Define the field.
Environmental Psychology examines how natural and built settings (noise, crowding, architecture, climate, green spaces) influence perception, emotion and behavior—and how humans impact environments (sustainability, pro-environmental action).
Step 2: Rule out close options.
Social psychology centers on interpersonal processes (attitudes, groups), not the {physical} environment per se. Child psychology focuses on development.
Step 3: Conclude.
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\boxed{\text{Option B}}
$$