The right answers are;
Mercury is one of the inner planets.
The inner planets are also called terrestrial planets.
Gases escaped from them during the planets’ formation.
Mercury, Venus, Earth and Mars are the four inner planets. They are also called terrestrial planets because they have solid and rocky surfaces similar to earth. The inner planets are much smaller than the outer planets (Jupiter, Saturn, Uranus and Neptune). The inner planets are composed of mainly heavy metals such as iron and nickel, and they do not have moons. During the inner planet’s formation, thick gas atmospheres are blown away .
