中山区

中 = 丨 + 口 : Mnemonic symbol: a dart board, because you always try to hit the center.

Julian Giant Squid (zhu-) is throwing dinosaur bones (丨) as darts on a dart board in front of the engine ((e)ng1). To make it a bit more difficult he's throwing mandarins (口) into the air as well and skewers them up right in the center (中 is a mandarin skewered on a dinosaur bone) in mid flight with the dinosaur bones. He's still able to consistently hit the center (中) of the dart board.

山 = 丨 + 凵 : Mnemonic symbol: 山 looks like the tip of a fork. Sherlock Holmes (sh) is climbing a mountain (山) in front of the anthill (an1). He uses a dinosaur bone (〡) as walking stick, and to have better grip he attached a fork (山) to its tip. Unfortunately he accidentally sticks the fork into a receptacle (凵) on the ground of the mountain and gets shocked.

區 = 匚 + 品 : Cupid receives a metal box in front of the space station. He opens it and finds a road sign with a pyramid on it. Clever as he is, he derives that it must have been sent to him from the region of Egypt.

区 = 乂 + 匚 : Mnemonic symbol: An alien from Area 51.

区 = 乂 + 匚 : Cupid is chilling in front of the space station, when an alien from Area 51 flies by and gives him a metal box. Unfortunately, even using pliers, Cupid is too weak to open it.