After watching television while surfing the Internet on your tablet, you find yourself having trouble falling asleep at night. According to what we know about the biology of sleep, what is the most likely cause of your sleep problem?

a. The bright screens are causing your pineal gland to release too much melatonin.

b. The TV shows are probably too exciting, making it difficult to calm down for sleep.

c. Surfing the Internet while watching television is too much for your brain, leading to poor sleep.

d. The bright light from the TV and tablet are interfering with your sleep–wake cycle.