Select the most appropriate meaning of the given idiom.

By leaps and bounds

Rapidly

The most appropriate meaning of the idiom "by leaps and bounds" is rapidly. This idiom means that something is improving or progressing very quickly. The image of leaps and bounds is one of movement that is sudden and unexpected, and so the idiom is used to describe something that is changing or developing very rapidly.

The other options for the meaning of the idiom are not accurate. To frighten means to make someone afraid. Ordinary means average or unremarkable. Invalid means not valid or not in effect.