When does a person attain fully insured status under Social Security?

When does a person attain fully insured status under Social Security?

A. after 40 quarters (10 years) of participation paying FICA taxes B. after 20 quarters (5 years) of participation paying FICA taxes C. after 30 quarters (7.5 years) of participation paying FICA taxes D. after 50 quarters (12.5 years) of participation paying FICA taxes