Which of the following are key characteristics of a gas giant planet?

Gas giants, such as Jupiter and Saturn, are characterized by their large size and thick atmospheres primarily made up of hydrogen and helium. Unlike terrestrial planets, gas giants do not have a well-defined solid surface; instead, their gaseous layers transition into denser materials beneath.

The significant mass of gas giants contributes to their strong gravitational pull, which helps retain the thick atmospheres—these atmospheres can be thousands of kilometers thick. Additionally, the lack of a solid surface is a defining feature; although it is believed that there may be solid cores at their centers, the outer layers consist of gas that becomes increasingly dense under pressure. This understanding reflects the fundamental nature of gas giants and distinguishes them from rocky planets, which are smaller, have solid surfaces, and often lack thick atmospheres.

In summary, the correct answer is supported by these key characteristics, which define gas giants both in terms of their physical structure and composition.