Question

Consider the following passage and choose the correct answer to the question given below it. The night sky our ancestors knew is fast disappearing. In many cities today barely a few dozen stars are visible to the naked eye, drowned out by the glare of streetlights, billboards and buildings. This "light pollution" does more than spoil a pretty view. Nocturnal creatures — moths, sea turtles, migrating birds — depend on darkness to navigate, feed and breed, and artificial light disorients them, sometimes fatally. Human health suffers too: bright light at night suppresses melatonin, the hormone that regulates sleep, and chronic disruption of sleep cycles has been linked to obesity, depression and heart disease. Astronomers, whose observatories keep retreating to remoter mountaintops, were among the first to sound the alarm. Yet the remedy is surprisingly simple. Shielded lamps that throw light downward, warmer-coloured bulbs, motion sensors and sensible switch-off timings can cut wasted light sharply without making streets less safe. A few cities that adopted such measures report energy savings of over thirty percent. Darkness, it turns out, is a resource worth conserving.

According to the passage, exposure to bright light at night affects human health by