求翻译：每隔四厘米取一个样品是什么意思？

Every four centimeters to take a sample

every 4 cm from one sample

Each four centimeters take a sample

Every four cm take a sample

Teaching building in the distance intervals can be seen hanging on the wall of the brand, is a brief introduction to the variety of rare animals such as: blue fire back, alias Swinhoe, for the specialty birds of Taiwan Province in China, the main Habitat in the mountain forests to 2700m above sea le