what's the correct answer and why?

1

No1 is the correct answer.

No 2 with being, makes this sentence hanging, thus not forming a complete sentence.
No 3. You need a subject for this sentence, thus, a subordinate clause starting with that cannot fit in this circumstance.
No 4 Being the earth is a gerund phrase, and is technically followed by a verb

I think 1 is the correct answer.

i think 1 is the correct answer

3-Earth is the third planet from the Sun and the fifth largest: ... Pluto is smaller than seven of the solar system's moon

that mean the answer should be like this.

Earth is the .....

the earth is the - is wrong.

hence all the 4 are wrong.

Deepak Chaliyaththat mean the answer should be like this.Earth is the .....the earth is the - is wrong.hence all the 4 are wrong.

Hi Deepak Chaliyath,
Not truth, your perception is incorrect. In fact, The Moon, the Sun and The Earth all require the definite article "the" in normal collocation. i.e

ok... understood. you are right...that means 1 and 2 are right.