Adverb of frequency.** "Hardly ever" is a phrase that indicates the frequency of the visits.

He runs slow.** The correct form should be "He runs slowly," as "slowly" is the adverb modifying "runs."

It modifies the adverb "softly."** "Very" is an adverb of degree, modifying another adverb, "softly."

Fast.** "Fast" is an adverb of manner, not time.

Where?** Adverbs of place answer the question "where?" by indicating the location of the action.

He quickly finished his work.** "Quickly" is an adverb of manner, describing how he finished his work.

Soon.** "Soon" is an adverb modifying the verb "arrive," indicating when she will arrive.

Often.** "Often" is an adverb of frequency, indicating how frequently an action occurs.

To describe the verb "ran."** The adverb "quickly" modifies the verb "ran" by telling us how the action was performed.

She sings beautifully**. "Beautifully" is an adverb that modifies the verb "sings," explaining how she sings.