What does the term heptachromic mean?

The term "heptachromic" refers to the ability to perceive seven different colors. This implies a heightened or enhanced capacity for color vision beyond the normal range. Therefore, the correct choice indicating "normal color vision" aligns with this definition as it suggests the ability to see a full spectrum of colors, including the additional colors perceived in a heptachromic condition.

In the context of the other options, a condition with altered color perception refers to any anomalies in color vision that fall outside of the normal range, such as color blindness or other color vision deficiencies, which does not accurately describe heptachromic vision. An absence of color perception points to complete color blindness, where no colors can be seen, which is also not applicable. Finally, difficulty in distinguishing colors generally pertains to various forms of color blindness or other vision issues that affect color discrimination, contrasting with the enhanced capability implied by heptachromic vision.