In this sentence improvement question, select the option that makes the sentence grammatically correct: He speaks so fast to be understood.

Introduction / Context:
This grammar question tests your knowledge of degree expressions and result clauses in English. The original sentence "He speaks so fast to be understood" sounds unnatural because it uses "so" incorrectly with an infinitive. Competitive exams frequently test the difference between "so ... that" structures and "too ... to" structures, both of which express ideas about degree and consequence.

Given Data / Assumptions:
- Original sentence: He speaks so fast to be understood.- The goal is to express that his manner of speaking makes it impossible for others to understand him.- Options are: "very fast to be understood", "too fast to be understood", "too fast that he cannot be understood", and "No improvement".- Only one option uses the correct grammatical pattern.

Concept / Approach:
When we want to say that something is so extreme that it prevents a result from happening, English typically uses the "too ... to" pattern: "too fast to be understood", "too heavy to lift", "too late to change". The "so ... that" pattern requires the word "that" and a clause: "so fast that he cannot be understood". The original sentence incorrectly mixes "so" with an infinitive "to be understood". Therefore, the correction must either use "too ... to" or "so ... that" with a complete clause. Among the options, only "too fast to be understood" follows a fully correct structure.

Step-by-Step Solution:
Step 1: Identify the intended meaning: his speed of speaking prevents understanding.Step 2: Recall that for this idea we use "too + adjective/adverb + to + verb", which expresses an excessive degree.Step 3: Apply this pattern to "fast" and "understand": "too fast to be understood".Step 4: Check option "very fast to be understood": "very" expresses high degree but does not combine naturally with "to be understood" to express impossibility.Step 5: Check option "too fast that he cannot be understood": This incorrectly combines "too" with "that"; the standard pattern is "so ... that", not "too ... that".Step 6: Observe that "No improvement" cannot be correct because the original sentence is unidiomatic.Step 7: Conclude that "too fast to be understood" is the correct improvement.

Verification / Alternative check:
You can compare with familiar sentences: "The music was too loud to sleep", "The bag is too heavy to carry alone", "He spoke so fast that nobody could follow him." In all these examples, the patterns are either "too ... to" or "so ... that". Notice that we never say "so fast to be understood". Therefore, the corrected version, "He speaks too fast to be understood", is fully consistent with standard structures in English.

Why Other Options Are Wrong:
Option "very fast to be understood": The word "very" intensifies "fast" but does not create a result meaning with an infinitive, so the phrase is ungrammatical.Option "too fast that he cannot be understood": Combines "too" with "that", which is incorrect; it should be "so fast that he cannot be understood".Option "No improvement": Incorrect because the original sentence misuses "so" with "to be understood".

Common Pitfalls:
Many learners confuse the patterns "too ... to" and "so ... that" and mix the elements incorrectly. They may write "so fast to" or "too fast that", both of which sound wrong to native speakers. Another pitfall is overusing "very" in places where a result or consequence needs to be expressed. To avoid such mistakes, memorise the correct structures: "too + adjective/adverb + to + verb" for excess leading to impossibility, and "so + adjective/adverb + that + clause" for strong degree leading to a result.

Final Answer:
The correct improvement is too fast to be understood, so the sentence should read: He speaks too fast to be understood.