Aflat character is defined by
only one or two traits
his complex hopes, dreams, flaws, thoughts, feelings, and motives
through words and actions

only one or two traits

A flat character is a simplistic character, displayed by the writer as possessing just one or two characteristics, which commonly persist similarly during the narrative, not experiencing notable growth or differences.

Flat characters are two-dimensional in that they are comparatively uncomplicated and do not vary during the course of work. By variation, round characters are complicated and experience development, sometimes adequately to confuse the reader.

it’s lava came from an explosive eruption

the answer is sex-linked recessive.