Question

which biological factor may be involved in the development of mental illness?
○ infections
○ left - handedness
○ height - weight ratio
○ birth order in a family

Explanation:

Infections can be a biological factor. They can cause inflammation, damage to the nervous system, or disrupt normal brain function, which may contribute to the development of mental illness. Left - handedness is a functional preference, height - weight ratio is a physical proportion related to growth and nutrition (not directly a biological factor for mental illness in the same sense as infections), and birth order is a social - environmental factor.

Answer:

infections