Answer:
What does a WW1 Trench, A Submarine and a Popular Phone App all have in common?
My sides are firmly laced about, Yet nothing is withinΝΎ You'll think my head is strange indeed, Being nothing else but skin.
Lovely and round, I shine with pale light, grown in the darkness, a lady's delight.
Goes over all the hills and hollows. Bites hard, but never swallows.
Up on high I wave away but not a word can I say.
What do angels sing in the shower?
Difficult
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?