Which method of copying digital evidence ensures proper evidence collection?

Comprehensive and Detailed Explanation From Exact Extract:

A bit-level (bitstream) copy creates an exact sector-by-sector duplicate of the original media, capturing all files, deleted data, and slack space. This method is essential to preserve the entirety of digital evidence without modification.

Bit-level imaging maintains forensic soundness.

It allows investigators to perform analysis without altering original data.