她用左脚轻轻按了按钮。

She pressed the button gently with her ___left foot.

她的建议直接来自L.F.，让所有人都措手不及。

Her suggestion came straight from ___L.F., catching everyone off guard.

这个收音机可以清晰地接收低频信号。

This radio can pick up ___LF signals clearly.