Answer:
An adult cosigner reason been that he is under 18
Explanation:
Based on the information give, since we were told that he is 16 years old in which he want to open a savings account which means that he will need to bring AN ADULT COSIGNER to the local bank branch in order to start an account reason been that he is under 18.
Hence, AN ADULT COSIGNER can either be his parent, his close family member or his friend who will stand for him because he is under 18.