单元 5 - 5B

The eye is a complex sensory organ that enables vision in humans. It consists of several parts working together to capture and process visual information. The front part of the eye includes the transparent cornea and the colored iris, which controls the amount of light entering the eye through the pupil. Behind the iris is the crystalline lens, which focuses light onto the retina at the back of the eye. The retina contains specialized cells called photoreceptors that convert light into electrical signals, which are then sent to the brain via the optic nerve. The eye also has structures such as the sclera, the white outer layer, and the conjunctiva, a thin membrane covering the front of the eye.

The cat is a small carnivorous mammal and a popular domestic pet known for its independent and agile nature. Cats are known for their graceful movements, keen senses, and hunting abilities. They come in various breeds, sizes, and colors, ranging from the elegant Siamese to the fluffy Maine Coon, and are known for their distinct personalities. Cats are known for their grooming habits, often spending significant time cleaning themselves, and for their ability to climb and jump with precision. They are also known for their playfulness, curiosity, and sometimes aloof demeanor. Cats are often kept as indoor pets and are known for their companionship, providing affection and comfort to their owners. They are skilled hunters and are known for their ability to catch rodents and other small prey. Cats have a strong sense of territoriality and are known to establish their own territory, often within their human homes. They require regular care, including grooming, vaccinations, and veterinary attention, and are cherished by many as beloved family members.

The dog is a domesticated carnivorous mammal and a close companion of humans, known for its loyalty, affection, and diverse breeds. Dogs are descended from wolves and have been selectively bred for thousands of years for various purposes, such as hunting, guarding, herding, and companionship. They come in many shapes, sizes, and colors, ranging from small toy breeds like Chihuahuas to large working breeds like Great Danes. Dogs have a keen sense of smell, sharp hearing, and excellent vision, which make them well-suited for a variety of tasks, including search and rescue, detection, and service work. Dogs are known for their playful and social nature, forming strong bonds with their human companions and often serving as beloved members of families. They require regular exercise, training, and care to thrive and are known for their unwavering loyalty and unconditional love for their owners.

A car is a type of automobile designed for personal transportation. It is powered by an engine, usually using gasoline or electricity, and typically has four wheels. Cars are commonly used for driving on roads and can carry passengers and sometimes small loads. They come in various shapes and sizes, such as sedans, hatchbacks, and SUVs, with different features like air conditioning, music systems, and safety equipment. Cars are essential for everyday travel, whether for commuting, errands, or long trips.