Answer:
What does a WW1 Trench, A Submarine and a Popular Phone App all have in common?
There are several different kinds, but the one you pick doesn't do its job. What is it?
What hangs others yet can unintentionally hang itself?
What can you catch but not throw?
Two brothers we are, great burdens we bear. All day we are bitterly pressed. Yet this I will say, we are full all the day, and empty when go to rest.
What do angels sing in the shower?