In the sentence "Simon teaches children __________ water colour painting", which option correctly completes the phrase "the art of water colour painting"?

Introduction / Context:
This question tests your understanding of a very common noun preposition combination in English: the art of something. The sentence Simon teaches children ________ water colour painting needs the correct prepositional phrase to indicate that he teaches the skill itself. You have to choose the phrase that is normally used to connect art with the activity that follows.

Given Data / Assumptions:

• Sentence: Simon teaches children ________ water colour painting.
• Intended meaning: Simon instructs children in the skill or technique of water colour painting.
• Options: the art on, the art in, the art by, the art of.
• We assume the standard pattern is the art of plus activity name.

Concept / Approach:
In English, when we refer to a skill or area of creative work, we use the expression the art of followed by a gerund or noun phrase. For example, the art of cooking, the art of negotiation, or the art of water colour painting. The prepositions on, in, and by do not normally follow the art in this sense. Therefore, the correct phrase is the art of, which accurately describes the subject that Simon teaches.

Step-by-Step Solution:
Step 1: Recognise that water colour painting is the skill or discipline being taught.Step 2: Recall the standard phrase the art of plus a noun or gerund to describe a skill.Step 3: Insert each option into the sentence and test: Simon teaches children the art of water colour painting sounds natural and clear.Step 4: Phrases like the art on water colour painting or the art in water colour painting do not appear in standard English usage.Step 5: Therefore, the only correct completion is the art of, giving a grammatically and idiomatically correct sentence.

Verification / Alternative check:
Look at similar examples: She teaches the art of classical dance, They study the art of photography, and He has mastered the art of public speaking. In each case, the preposition of links art and the following activity. Trying to substitute on, in, or by produces unnatural expressions that would not be acceptable in a formal exam. This consistent pattern confirms that the correct preposition is of.

Why Other Options Are Wrong:
The art on suggests a topic or subject of a written piece, as in an article on something, but that is not how we describe skills. The art in could possibly be used in a different structure, such as the art in this painting, but not in the phrase the art in water colour painting. The art by is used to attribute artwork to an artist, as in art by Van Gogh, which is also unrelated to the intended meaning. None of these alternatives fits the structure of the sentence as given.

Common Pitfalls:
Prepositions often cause confusion because many of them can appear in a wide variety of phrases. Students may be tempted to choose on or in simply because they see them frequently. However, certain noun preposition collocations like the art of or the risk of are fixed and should be learned as whole units. Memorising these patterns helps avoid hesitation and errors in the exam.

Final Answer:
The correct phrase is the art of, so the sentence should read Simon teaches children the art of water colour painting, and option D is correct.