The blackout period refers to

A$)$ The period from the time when the youngest child reaches age $16$ to the time when the spouse attains age $65.$

B$)$ The period from the time when the youngest child reaches age $18$ to the time when the spouse attains age $60.$

C$)$ The period from the time when the youngest child reaches age $16$ to the time when the spouse attains age $60.$

D$)$ The period from the time when the youngest child reaches age $18$ to the time when the spouse attains age $65.$