Earth's seasons are caused by the earth's tilt on its axis.
The Olmec civilization had a parent culture of many of the Mesoamerican cultures that came after; such as, the Mayans and Aztecs, and eventually built a large network through Mesoamerica. They traded (obsidian knives, animal skins, and salt), their religion was of the cosmos and belief of an underworld and earth had certain characteristics.Their religion aspects led to mythology and their art was far ahead of their time. Also, they were the first engineers of America (Ex. Aqueduct of San Lorenzo), and its military mights.
From reading the document, it can be gathered that the Great Leap Forward caused Shanghai to plunge into economic turmoil, it resulted in critical food shortages and hunger, and it caused many to attempt to leave the country out of desperation.
The ear is divided into three main parts the outer ear, the middle ear, and the inner ear. The inner ear is filled with fluid. The inner ear also contains the receptors for sound which convert fluid motion into electrical signals known as action potentials that are sent to the brain to enable sound perception.