孩子们在沙滩上堆沙堡。

The children are building ___castles in the sand.

这些城堡的高墙曾经保护着中世纪的城市。

The thick walls of these ___castles protected medieval towns.

在第五步棋时，她用车王易位来加强防守。

On her fifth move, she chose to ___castle to strengthen her defense.