Important points: 1. Early mammals spent most time in low light
2. Mammals today adapted to dim lighting
3. Bright artificial light
likely to interfere with sleep
Exploring the options:
A - Explicitly states that more time in bright light equals irregular sleep, does not specify it as a likely scenario, hence no.
B - No difference given between artificial or natural light effects in the biologist's statement, hence no.
C - Sleep cycle depends, at least in part, on environmental conditions as stated by biologist giving example of lighting conditions, hence likely answer
D - No mentions of healthier sleep anywhere in the paragraph, hence no
E - Intensity of light is nowhere mentioned in the paragraph, hence no.
Answer C