Which of the following is/are TRUE? (The answer may have both above)

a. Social Security taxes withheld and income taxes withheld are required payroll deductions.

b. Social Security taxes are an optional deduction from employee earnings.

c. Social Security taxes are a deduction from employee earnings and are also imposed upon employers as an expense.

d. The employer incurs payroll tax expense equal to the amount withheld from the employees' wages for income taxes.