Answer:
The answer that I think would be correct is option C (survivors benefits)
Step-by-step explanation:
Retirement benefits definition: a form of social insurance payment made by the US Social Security (for age 62 and older) considering that Mary has two small kids, she probably isn't that old.
Disability benefits: in order to be eligible, you have to be unable to do regular or customary work for at least right days. Considering the fact that Mary is a stay at home mother then she wouldn't be employed.
Survivors benefit: this allows a retiree to ensure after death, a continuous lifetime annuity for their dependents.
Workers compensation: provision of benefits to employees who suffered work related injuries. Mary's husband most likely didn't die in the work place.