老式收音机可以接收低频信号。

Old radios can pick up ___LF signals.

乐谱上标记了ff表示这个小节需要演奏得响亮有力。

The sheet music has ___ff marked to indicate this section should be played loud and forceful.

银行要求首付至少20%，这意味着LF不能超过80%。

The bank requires at least 20% down payment, which means the ___LF cannot exceed 80%.