Scientists have concluded that Earth became solidified about 4.6 billion years ago.

a. True

b. False

a. True

Explanation:

Scientists concluded that 4.6 billion years ago, an object about the size of Mars hit Earth. As a result of the massive impact of this object's fall, about 30 to 65 percent of the earth melted into an outer layer hundreds of kilometers thick, which they called the "lava ocean" (molten rock). Similarly, the interior warmed to a "mild" (less dense) state, in which its components could move from side to side. The heavy material plunged inward to take the core and the lighter material floated to the surface and formed the crust. The emergence of the lighter material carried internal heat to the surface from where it could radiate into space. In this way the earth cooled and much of it solidified and was transformed into a differentiated or zoned planet into three main layers: core (inner and outer), mantle and crust.