Final answer:
Venus has the densest atmosphere in the inner solar system, composed primarily of carbon dioxide, which leads to high surface pressure and temperatures.
Step-by-step explanation:
In the inner solar system, the body with the densest atmosphere is Venus. Despite the massive sizes and deep atmospheres of the gas giants like Jupiter and Saturn, their atmospheres are composed chiefly of light gases such as hydrogen and helium, with Jupiter having the most massive among them. Venus, on the other hand, has a very thick and dense atmosphere composed predominantly of carbon dioxide, with a surface pressure about 92 times that of Earth's. The dense atmosphere of Venus creates a runaway greenhouse effect, leading to exceedingly high surface temperatures