为社么180-foot-high learning tower要加"-"但是It is about twelve metres high 不加"-"社么情况下才加"-"

问题描述:

为社么180-foot-high learning tower要加"-"
但是It is about twelve metres high 不加"-"社么情况下才加"-"

加上 -表示把它作为一个形容词.所有的复数都要变成单数.下一句中不需要做形容词因此就不加“-”了.如果要加-,就变成了It is a 12-metre-high ...