Failblog posted this amusing homework assignment, and someone in the comments pointed out that if you Google all five of the terms, you get taken to this page [spoiler!], which probably posted it originally and has access to the answer key. (The assignment is apparently from Russia, yet in English.)
I won’t post the real answer (which I argue is wrong), but by far my favorite (inaccurate) one:
They’re all completely screwed.
The penguin is standing in front of a train.
The boot has no foot in it.
The train has no tracks.
The whale is stranded out of the water.
The piano has no bench (nobody wants to play a piano without a bench…)
What do you think the commonality is?