Step 1: Recall the parts of a GIS.
A GIS is built from several subsystems that handle data capture, storage, management, analysis and output.
Step 2: Focus on the data capture subsystem.
Data capture is the very first stage, where the system brings information into the GIS.
Step 3: Rule out transformation.
Transforming data, such as changing its projection, is a later processing job, not the job of capture.
Step 4: Rule out storage and retrieval.
Storing data elements and retrieving them are separate functions handled by the storage and management subsystems.
Step 5: Match the capture function.
The data capture subsystem's main work is to bring in or acquire the spatial and attribute data.
Step 6: State the answer.
The data capture subsystem primarily performs acquiring data.
\[ \boxed{\text{Acquiring Data}} \]