Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the best answer to each of the following questions from 23 to 30.

Sleep is an essential part of life, playing a crucial role in maintaining overall health and well-being. Experts recommend that adults get at least seven to eight hours of sleep per night. During sleep, the body undergoes various processes to repair tissues, consolidate memories, and regulate hormones. Poor sleep can lead to health problems such as obesity, heart disease, and a weakened immune system. It also affects mental health, increasing the risk of depression and anxiety.

One key element of good sleep is maintaining a consistent sleep schedule. Going to bed and waking up at the same time every day helps regulate the body’s internal clock, known as the circadian rhythm. Disrupting this rhythm, such as through irregular sleep patterns, can lead to sleep disorders and decreased daytime alertness. Additionally, environmental factors like light, noise, and temperature play a role in sleep quality.

Some people struggle with insomnia, a condition that makes it difficult to fall or stay asleep. Common causes include stress, poor sleep habits, and medical conditions. Treatment options for insomnia include lifestyle changes, cognitive behavioral therapy, and, in some cases, medication. Experts often recommend limiting screen time before bed, as blue light from devices can interfere with the production of melatonin, the hormone that regulates sleep.

In recent years, there has been a growing awareness of the importance of sleep in improving productivity and overall quality of life. Employers and schools are beginning to consider sleep-friendly policies, such as flexible hours and later start times, to help people get the rest they need. With these changes, society is slowly recognizing that sleep is not a luxury, but a necessity.

The word "it" in paragraph 1 refers to _______.