Which does not occur at the continental margin in the Pacific Ocean? 1. widened margins
2. volcanic activity
3. earthquakes
4. plate interactions

Widen Margins occurs at the continental margin in the pacific ocean, so the answer is:

1. Widened Margins.

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.