Answer: Common disaster clause
Explanation:
Based in the information given in the question, the policy provision that will protect the rights of the contingent beneficiary to receive the policy benefits is the common disaster clause.
According to the common disaster clause, the primary beneficiary must survive the insured usually by a period of 30-90 days and if this doesn't happen, the benefit will be paid automatically to the secondary beneficiary.
The common disaster clause simply explains that even though there's an accident which leads to the death of the insured and the beneficiary, it'll be possible to determine that it was the beneficiary whom died last and the benefit will be given to the person accordingly.