Final answer:
The percentage of American workers covered by the Social Security system, according to the provided commentary, is approximately (b) 67 percent.
Step-by-step explanation:
According to the commentary provided, the percentage of American workers currently covered by the Social Security system is best reflected in the supplementary data which indicates that Social Security now provides benefits to over 48 million Americans and is the main source of economic survival for two-thirds of the elderly population. Given that two-thirds equates to approximately 66.67 percent, the closest answer choice from the given options to the percentage of American workers covered would be (b) 67 percent.