In this grammar error spotting question, the sentence is divided into three labelled parts followed by a No error option. You must decide which part is grammatically incorrect. The sentence reads: So soon as I shall (A) reach office, I shall (B) mail you the documents. (C) If you believe the sentence is correct, you should choose option (D) No error.

Introduction / Context:
This question tests your understanding of correct tense usage in conditional and time clauses in English. The sentence describes what will happen when a certain future event takes place, namely when the speaker reaches the office. In standard English, a future time clause introduced by as soon as normally uses the simple present tense, even though it refers to the future. The main clause uses a future form like will or shall. You must identify which part of the sentence breaks this rule.

Given Data / Assumptions:

• The sentence is broken into parts: So soon as I shall (A) reach office, I shall (B) mail you the documents. (C)
• Part (D) represents the choice No error.
• The intention is to say that the speaker will mail the documents immediately after reaching the office.
• The reporting style is formal examination English, where shall is used with I in the main clause.
• You must find the part that needs correction to follow established grammar rules.

Concept / Approach:
In English, time clauses introduced by words like when, as soon as, before, or after usually take the simple present tense when referring to the future, while the main clause takes the future tense. The correct pattern is As soon as I reach the office, I will mail you the documents. The phrase So soon as is itself less common than As soon as, and the use of shall in the time clause So soon as I shall reach is incorrect. The main clause I shall mail you the documents is acceptable in formal style. Therefore, the error lies in part (A).

Step-by-Step Solution:
Step 1: Examine part (A) So soon as I shall. This part combines the phrase So soon as with the future auxiliary shall, which is not standard in a time clause. Step 2: Recall the correct rule: we use the simple present after as soon as for future time reference, so we expect as soon as I reach, not as soon as I shall reach. Step 3: Examine part (B) reach office, I shall. This part contains reach office and I shall, where reach office completes the time clause and I shall begins the main clause. The phrase reach office could be made more natural as reach the office, but in many exam questions, omission of the article is tolerated and is not usually treated as the tested error here. Step 4: Examine part (C) mail you the documents. This part is grammatically correct and completes the main clause. Step 5: Combine the corrected version of the sentence: As soon as I reach the office, I shall mail you the documents. Here, only the time clause has been corrected by removing shall and using the simple present reach. Step 6: Conclude that part (A) contains the key error, because the auxiliary shall must not be used in the time clause after So soon as.

Verification / Alternative check:
Test the sentence by replacing shall with the simple present form: As soon as I reach the office, I shall mail you the documents. This version is both natural and rule based. If you keep So soon as I shall, the sentence sounds wrong to a trained ear and conflicts with standard grammar rules taught for time clauses. This confirms that the error is located in part (A).

Why Other Options Are Wrong:
Part (B) reach office, I shall roughly follows the expected structure, with reach as the main verb of the time clause and I shall introducing the future in the main clause, so it is not the focus of this question.
Part (C) mail you the documents is a correct and common phrase meaning send you the documents by email or post.
Part (D) No error is incorrect because we have identified a clear violation of the tense rule in time clauses in part (A).

Common Pitfalls:
Learners often make the mistake of using future auxiliaries like will or shall in time or conditional clauses because they are thinking directly in terms of future meaning. Examinations deliberately test this habit, so it is important to remember that words like when, as soon as, before, and after usually take the simple present, even though they refer to the future. Another pitfall is to be distracted by smaller stylistic issues, such as the missing article before office, and overlook the more fundamental tense error.

Final Answer:
The incorrect part is So soon as I shall, which should be As soon as I reach, so the correct choice is Part (A) So soon as I shall.