飞行员使用高频无线电与地面保持联系。

Pilots use ___HF radios to stay in contact with the ground.

实验室里处理HF时需要特别小心，因为它有很强的腐蚀性。

Special care is required when handling ___HF in the lab due to its high corrosiveness.

这种耐高温金属中添加了微量的铪以提高性能。

This heat-resistant metal contains small amounts of ___Hf to enhance its performance.