Which statement is true about Medicare Part B premiums?

Medicare Part B premiums can vary based on income, which is why this statement is accurate. The standard premium amount is adjusted depending on the beneficiary's modified adjusted gross income (MAGI) from the previous tax year. Higher-income individuals may pay a higher premium, known as the Income Related Monthly Adjustment Amount (IRMAA), which is designed to contribute a more equitable amount to the Medicare program based on one’s ability to pay.

The other statements do not properly reflect the nuances of Medicare Part B payments. For instance, the assertion that premiums are always a fixed amount of $100 a month is misleading, as this figure is outdated and does not account for annual adjustments. Saying that premiums are waived for retirees is also incorrect since retirees are generally expected to pay premiums for Part B unless they qualify for specific exemptions, such as certain low-income assistance programs. Lastly, Medicare Part B does not cover dental services; this coverage generally falls under separate dental plans, making this statement inaccurate as well. Thus, the variation of Part B premiums based on income is the key detail that makes the correct statement valid.