Which sampling method gives every item an equal chance of selection, aiming for an unbiased picture?

Answer: A. Random sampling

SP 800-55v1 gives every item the same chance of being picked under random sampling, the point being to end up with a picture that is not skewed.

Source: NIST SP 800-55 Vol. 1 (NIST) — Sec. 2.1 Measurement and Quantitative Assessment