Qurat, you're actually too selfish. That's why you're just talking about 'me'. Hahaha!!
Well dear, thanks for pointing it out. I was in hurry while I was replying so didn't pay attention to the later part.
@ Ghayas:
The explanation I posed in my reply was actually for you.
World = Duniya
Earth = Zameen
As qurat pointed out, zameen mein nahin zameen 'pe' hota hai. That's why the correct answer is 'on'.
Agar world (Duniya) hota to phir aap ka javab theek hota.
Regards,