Lenny, a support worker, has been assigned to help a family with their newborn. Which of the following statements about cribs and crib linens is correct?

Select one:

a$.$ The crib mattress should be soft and comfortable.

b$.$ The mattress must fit snugly inside the crib.

c$.$ The mattress must be at least $45cm(20$ inches$)$ lower than the top of the crib rails.

d$.$ Bumper pads should be used until the baby is $12$ months old.