The first atmosphere of Earth was made mostly ofGroup of answer choicesHeliumOxygenMethaneCarbon dioxide

The first atmosphere of Earth, known as the primordial atmosphere, was primarily composed of gases like hydrogen and helium, along with trace amounts of other gases. However, among the answer choices provided, carbon dioxide is the most relevant choice when considering the early conditions of Earth's atmosphere after it began to evolve.

During the formation of Earth around 4.5 billion years ago, it is believed that the initial atmosphere was lost due to solar winds and was later replaced by volcanic outgassing. This process released various gases, including carbon dioxide, water vapor, methane, and ammonia. The second atmosphere, heavily influenced by volcanic activity, contained much more carbon dioxide compared to the modern atmosphere, which is rich in nitrogen and oxygen.

Thus, taking these factors into account and based on the choices provided, the answer that most accurately represents the dominant gas in the Earth's early conditions would be Carbon Dioxide.