The refundable Young Child Tax Credit is available to taxpayers who qualify for the CalEITC and who have at least one qualifying child who is younger than what age?

a. Six years old as of the last day of the taxable year.

b. Sixteen years old as of the last day of the taxable year.

c. Seventeen years old as of the last day of the taxable year.

d. Twenty-four years old and a full-time student as of the last day of the taxable year.