Question

A flat character _____.

is a well-developed character
changes, or grows, according to occurrences in his life
has only one or two developed traits

Answer 1

has only one or two developed traits

Step-by-step explanation:

Answer 2

Flat characters do not change throughout the story, therefore it can not be "changes, or grows, according to occurrences in his life". Flat characters are also not that complicated so that means it can't be "is a well-developed character "...
Which means the correct answer is
"has only one or two developed traits"