Step 1: Think about what problem simple random sampling was designed to solve in the first place. Before probability sampling, investigators picked units by personal judgment, which often reflected conscious or unconscious preferences.
Step 2: SRS replaces personal judgment with a random selection mechanism, so the investigator has no control over which specific units get chosen. Each unit's inclusion depends only on chance, not on who is doing the selecting.
Step 3: This mechanical, impartial process is what "freedom from human bias" means, and it is the property that allows valid probability statements (standard errors, confidence intervals) to be made about the sample.
Step 4: None of the other listed properties, lower variance, guaranteed representativeness, or ease with large populations, are actually guaranteed by SRS; in fact these are sometimes better achieved by other sampling designs such as stratified sampling.
Step 5: So the one property that SRS uniquely and reliably delivers is objectivity in selection.\[\boxed{\text{Freedom from human bias}}\]