Final answer:
If Grandma owns a policy on her grandchild and dies, the 'payor benefit rider' would ensure the premiums are waived until the grandchild can take over the payments.
Step-by-step explanation:
The rider that would kick in if Grandma should die tomorrow is the payor benefit rider. This rider is commonly added to life insurance policies taken out on the life of a minor, where the policy owner is responsible for the premiums. If the policy owner (grandma in this case) passes away, the payor benefit rider ensures that the premiums are waived until the minor (the grandchild) reaches a certain age and is able to take over the payment of the premiums. Without this rider, the policy might lapse if no other arrangements are made for the premium payments after the policyholder's death.