Personality may be influenced by:
a.
birth order
b.
characteristics of the parents
c.
both a and b

d.
neither a nor b

The correct answer is C.

Birth order has a powerful impact  upon the child's emotion and may influence the development of its personality. The first born has the parents' undivided attention and often benefits emotionally from this experience, growing up to be more secure and self confident. The downsize of being a first born is the fact that the inexperienced parents may have very big expectation for the child and the child may end up feeling very pressured.

The second or third born children enjoy calmer and more experienced parents but they may feel inadequate because of the presence of the older sibling who does many things better. This experience makes the middle children more competitive.

The last one to be born is usually the most spoiled one and he may not be as ambitious as his siblings.

Some personality traits are hereditary so they may influence the child's personality. Among the traits found most strongly determined to be hereditary are ambition, vulnerability to stress, leadership, risk-seeking and respect for authority. The genetic factor for these traits is in the region of 50 to 60%.