When children start using language to ask about things, events and phenomenon around them, which of the following functions of language is used more than the others ?

The correct option is Heuristic.

Explanation:

In Michael Halliday's theory of language development, children use language to serve various functions as they grow and interact with their environment. These functions categorize how young children use language before and during the development of full adult syntax.

The primary functions include:

1. Heuristic function: This function of language is used to explore, learn, investigate, and seek knowledge about the environment. When children use language to ask questions like "Why?", "What is that?", or "How does this work?", they are actively using the heuristic function to acquire information and understand things, events, and phenomena around them.

2. Informative function: This involves communicating information, facts, or reporting events to others (e.g., "I have a new toy").

3. Imaginative function: This is used to create a world of play, tell stories, pretend, or express creative ideas.

4. Regulatory function: This is used to control or influence the behavior of others (e.g., "Do as I tell you", "Pick up the ball").

Therefore, when children start asking questions about things and events around them to learn and explore, they are primarily using the Heuristic function of language.