Answer:
What does everyone know how to open but not how to close?
What does a WW1 Trench, A Submarine and a Popular Phone App all have in common?
Round as an apple, deep as a cup, and all the kings' horses can't fill it up. What is it?
Something wholly unreal, yet seems real to I. Think my friend, tell me where does it lie?
I have a neck but no head. I have a body but no arm. I have a bottom but no leg.
Why was the cook arrested?