Good Riddles

Question: Without one or the other both would not exist. what i'm I ?

Question: I'm the son of water, but when I return to water, I die. Who am I?

Question: Vanitha goes to park on oct 2 sunitha on oct 3 ramya on oct4 sheela on oct 5 on which date all four friends meet at the park.

Question: What can be dying but not be dying?

Question: I am unseen but all people know of me. I am intangible yet sharper than any sword. I come from nothingness but can fell even the mightiest kings.