Which of the following is not an environmental crisis?

Which of the following is the biggest of all?

The universe started ……………… ago.

…………… is the path of the earth around the sun.

Earth travels around the sun at a speed of …………….. per hour.

Earth takes ………………. days to complete one revolution.

The Earth began to form around years ago.

Which of the following came into existence first?

The radius of the earth is ………….

Top layer of the earth is called.