extra-dense flint

例句：

1. 1. The extra-dense foam cushioned the impact ofthe fall.
   超密度的泡沫缓冲了跌落的冲击。
2. 2. Extra-dense fiberglass isused in construction to increase strength and durability.
   使用超密度玻璃纤维在建筑中增加强度和耐用性。
3. 3. The extra-denselayer of snow made it difficult for thehikers to move forward.
   超密度的雪层使徒步旅行者难以前进。