From the given options, choose the one which gives the correct meaning / explanation for the expression

To beat the air

To make vain efforts

The correct answer is > To make vain efforts.

The idiom to beat the air means to make futile or useless efforts. It is often used to describe someone who is trying to achieve something that is impossible or very difficult. The idiom comes from the image of someone flailing their arms about in the air, but not actually making any progress.

In the sentence, the speaker is saying that they are beating the air, which means that they are making futile efforts to achieve something. This is why the idiom to beat the air is used in this context.

The other options are incorrect.

• To brag and boast is not correct because the idiom to beat the air does not refer to bragging or boasting.
• To submit to a stronger force is not correct because the idiom to beat the air does not refer to submitting to someone or something.
• To acknowledge defeat is not correct because the idiom to beat the air does not refer to acknowledging defeat.