Final answer:
Venus, although similar in size and mass to Earth, has an atmosphere drastically different with 96% carbon dioxide and conditions resulting from a runaway greenhouse effect.
Step-by-step explanation:
The statement about Venus having an atmosphere whose composition is similar to that of Earth is false. Although Venus is indeed referred to as Earth's twin due to its similar size and mass, and while there might be expectations for geological similarities, Venus' atmosphere is substantially different from Earth's. The atmosphere of Venus is composed primarily of carbon dioxide (CO₂), which accounts for 96% of the atmosphere, with a high surface pressure nearly 100 times greater than Earth's. Additionally, the surface temperature on Venus is extremely high, estimated at 730 K (over 850 °F). These conditions are vastly different from the earthlike conditions we experience on our home planet, primarily due to a runaway greenhouse effect that led to the current hostile environment on Venus. Understanding the stark differences between the atmospheres of Earth and Venus remains an important challenge in planetary science.