Question

studying takes time, but it usually produces positive results.
participle infinitive gerund

Explanation:

In the sentence "Studying takes time, but it usually produces positive results", the word "Studying" functions as a gerund. A gerund is a verb form ending in -ing that acts as a noun. Here, "Studying" is the subject of the sentence, acting as a noun (referring to the action of studying), so it is a gerund. A participle would function as an adjective or part of a verb phrase, and an infinitive is in the form "to + verb", which is not the case here.

Answer:

gerund