The TOEFL iBT examination has four sections Reading, Listening, Speaking and Writing. In the fourth section you write an essay on one topic. What is the main purpose of this TOEFL iBT essay writing task?

Introduction / Context:
This question is about the structure of the TOEFL iBT examination, which is widely used to assess English language proficiency for academic admission. The exam has four sections, and the fourth section requires the test taker to write an essay. Understanding the purpose of this essay task is important for students preparing for international tests as well as for general awareness about standardised exams.

Given Data / Assumptions:
- The TOEFL iBT has four sections: Reading, Listening, Speaking and Writing.
- The fourth section is Writing and involves writing an essay on one topic.
- Options describe different possible purposes, such as testing handwriting, multiple choice grammar, speaking or diagram drawing.
- We assume the test is delivered via computer, as in the internet based TOEFL format.

Concept / Approach:
The main purpose of the TOEFL iBT writing task is to evaluate academic writing skills. Specifically, the exam measures how well a candidate can organise ideas, express an opinion, support it with reasons and examples, and use appropriate grammar and vocabulary within a time limit. It is not about handwriting quality or drawing, and speaking is assessed in a separate section.

Step-by-Step Solution:
Step 1: Recall that TOEFL iBT is administered on a computer, so handwriting is not a focus. Step 2: Know that the writing section requires composing essays in English using a keyboard. Step 3: Understand that the scoring rubrics emphasise organisation, clarity of argument, coherence, and language accuracy. Step 4: Match this understanding with the option that describes writing an organised essay expressing and supporting an opinion within a time limit.

Verification / Alternative check:
As another check, consider that grammar is tested across all sections, not just through multiple choice questions. Speaking is measured with tasks where you talk into a microphone, so any option describing speaking belongs to the Speaking section, not the Writing section. Diagrams and charts are not part of TOEFL iBT tasks, which confirms that the essay task is focused on structured writing and argumentation.

Why Other Options Are Wrong:
The option about handwriting is wrong because TOEFL iBT uses typed responses and does not evaluate penmanship.
The multiple choice grammar option is incorrect since grammar is integrated into reading, listening, speaking and writing, but the writing section does not consist of only grammar questions.
The speaking based option is wrong because it confuses the writing section with the speaking section.
The diagram drawing option is incorrect because the exam does not include tasks where candidates draw charts or figures.

Common Pitfalls:
Some students may think that the writing section is only about correct grammar and therefore underestimate the importance of structure and coherence. Others may confuse computer based test formats with older paper based tests where handwriting could matter. Understanding the evaluation criteria of standardised exams helps candidates prepare efficiently and answer such questions correctly.

Final Answer:
Therefore, the main purpose of the TOEFL iBT essay writing task is to write an organised essay expressing and supporting an opinion on a given topic within a time limit.