In the following sentence, choose the most appropriate clause to complete the blank so that the result is expressed correctly: He ran so fast _________.

Introduction / Context:
This question checks understanding of cause and result clauses in English, particularly the pattern so plus adjective or adverb followed by that plus clause. Exam candidates are expected to recognise that He ran so fast introduces a cause and that the following part must express the result in correct tense and structure. Such questions are common in competitive exams because they test grammar, sentence structure, and the ability to distinguish between similar looking connectors like so and that.

Given Data / Assumptions:

The sentence stem is: He ran so fast _________.

We need a clause that shows the result of running very fast.

Options provide different connectives and verb forms.

The context is a past event, indicated by ran.

Exactly one option should be fully correct and natural.

Concept / Approach:

In English, the pattern so plus adverb or adjective plus that plus clause is used to show cause and effect. The structure is: subject + verb + so + adverb or adjective + that + result clause in the appropriate tense. Here, so fast is the cause; the result clause should be in the past tense because the main verb ran is in the past. Options that break this pattern, change the tense inappropriately, or lack a connector needed for a complete clause must be rejected.

Step-by-Step Solution:
Step 1: Identify the pattern: He ran so fast suggests that a that clause of result should follow. Step 2: Test option a: that he fell. The full sentence becomes He ran so fast that he fell, which is grammatically correct and clearly expresses the result of running very fast. Step 3: Test option b: so he fell. He ran so fast so he fell is awkward because the repetition of so is unnatural; the sentence does not follow the standard result pattern. Step 4: Test option c: he fell. He ran so fast he fell is sometimes heard in speech, but in formal exam English it is considered incomplete without that. Step 5: Test option d: that he is falling. This mixes past and present progressive tenses and does not match the completed event described by ran. Step 6: Test option e: in order that he falls. This expresses purpose rather than result and uses an unsuitable present tense. Step 7: Conclude that option a best fits both the grammar rule and the natural expression of cause and effect.

Verification / Alternative check:

We can verify by comparing with similar sentences. For example: She spoke so softly that nobody heard her or The task was so difficult that many students gave up. In each case, the main verb is in the past tense and the result clause is also in the past. Our sentence He ran so fast that he fell follows exactly the same pattern. Therefore, option a is fully consistent with standard usage and exam expectations.

Why Other Options Are Wrong:

Option b (so he fell) is clumsy and repeats so, which breaks the normal pattern of so fast that.

Option c (he fell) lacks the connector that and sounds informal or incomplete for an exam setting.

Option d (that he is falling) uses a present continuous tense which does not match the completed past action.

Option e (in order that he falls) expresses purpose rather than result and is therefore inappropriate here.

Common Pitfalls:

Many learners confuse the use of so that for purpose with so adjective that for result. They may also ignore tense consistency and select a present tense result clause after a past verb. Another frequent problem is overlooking the role of that as a conjunction that introduces a full clause. For exam questions, it is important to select the fully standard and formal structure even if a shorter spoken form appears possible.

Final Answer:

The correct clause to complete the sentence is that he fell.