The inner planets mercury, venus, earth, and mars were formed by

ANSWER:

About some billion years ago, dust and gas particles began orbiting around the sun. These particles then began to stick together and formed large particles. Slowly, these particles began attracting more mass with their gravity. After millions of years, these particles became planetesimals. They started revolving around the sun in their own orbit and formed spherical shapes. This continued for another millions of years and thus planets were formed.

EXPLANATION:

The inner planets are the four planets that are closest to the sun. The inner and outer planets are separated by asteroid belts. The "inner planets are terrestrial" and rocky whereas the "outer planets" are mostly gas.