Which of the following is NOT a characteristic shared by Venus and Earth?

The choice indicating that Venus and Earth have significantly different sizes is correct because while there are differences in their dimensions, they are not as extreme as the options suggest. Venus has a diameter of about 12,104 kilometers, while Earth’s diameter is approximately 12,742 kilometers. This makes Venus about 95% of Earth's diameter, indicating that they are quite similar in size.

In contrast, both Venus and Earth share a solid surface, which allows for geological features such as mountains and valleys. Both planets also possess a dense atmosphere; Venus's atmosphere is thick with carbon dioxide, leading to a strong greenhouse effect, while Earth’s atmosphere, although different in composition, is still dense enough to support weather and life. Furthermore, the gravitational forces on both planets are relatively similar, with Venus having about 91% of Earth's gravity, which allows for comparable physical effects on objects in a gravitational field.

Therefore, the significant similarity in size between Venus and Earth is what sets the correct answer apart from the other characteristics that they do share.