Question

Which object donot cast shadow

Answer 1

A transparent object will not make any shadow, as light will pass straight through it.

Answer 2

A fully transparent object will not cast shadow.

But I am not sure if you can find such a transparent object. Even glass will cast some faint shadow.

One thing that will not cast shadow for sure is fire. Light a match stick and hold it in sunlight. You can see the shadow of the wooden match stick but no shadow of fire.