Let's analyze the given sentence to identify the grammatical error: "Since India has started doing well in hockey it had once again become a popular sport."

The sentence connects two ideas:

1. India's recent improvement in hockey ("has started doing well").
2. Hockey becoming a popular sport again ("it had once again become a popular sport").

The first clause, "Since India has started doing well in hockey," uses the present perfect tense ("has started"), which indicates an action that began in the past and has a connection to the present. It suggests that the improvement is ongoing or its effects are currently felt.

The second clause, "it had once again become a popular sport," uses the past perfect tense ("had become"). The past perfect tense is typically used to describe an action that happened before another past action or a specific point in the past. For example, "By the time I arrived, the train had already left."

In the given sentence, the popularity of hockey is presented as a result or consequence of India's recent performance. The use of "has started doing well" in the first clause refers to a recent state or ongoing action. Therefore, the resulting popularity should logically be described in a tense that reflects this connection to the present or the recent past.

Let's examine the options provided and the specific segment indicated as having the error:

• Option 1: become a popular sport - This is the latter part of the predicate. Standing alone, this segment isn't the root of the tense mismatch.
• Option 2: it had once again - This segment contains the auxiliary verb "had," which forms the past perfect tense when combined with "become." The issue lies in the use of "had" in this context following "has started."
• Option 3: doing well - This is part of the present perfect continuous construction "has started doing well," which is grammatically correct in itself and fits the context of ongoing improvement.
• Option 4: Since India - "Since" is used here to introduce a reason or cause, which is a correct usage. "India" is the subject. This segment is grammatically sound.

The error is in the use of the past perfect "had become" after a clause using the present perfect "has started." The popularity of hockey is a consequence of the recent performance. A more appropriate tense for the second clause would be the present perfect ("has become") to show that the popularity is a result of the recent improvement and its effect is felt now, or the simple past ("became") if the focus is simply on the point in time the popularity was regained.

Comparing "has started" and "had become", the tenses are mismatched. The action of becoming popular follows and is caused by the action of starting to do well. Using "had become" suggests that becoming popular happened before some other past event, which is not implied here.

Therefore, the segment "it had once again" contains the grammatical error because "had" is the incorrect auxiliary verb given the tense of the preceding clause and the intended meaning.

Corrected sentence structure could be: "Since India has started doing well in hockey, it has once again become a popular sport." (using present perfect in both clauses)

Let's summarize the analysis of the options:

Revision Table: Understanding Tense Consistency

Maintaining consistent and logical tense usage is crucial for clear communication. Here's a quick look at tenses involved:

• Present Perfect (has/have + past participle): Used for actions that started in the past and continue to the present, or actions completed in the past with a present result.
• Past Perfect (had + past participle): Used for actions completed before another past action or a specific point in the past.

In the original sentence, the cause ("has started doing well") is in the present perfect, implying a connection to the present. The effect ("had once again become popular") uses the past perfect, incorrectly suggesting it occurred before some other past event, rather than as a result connected to the present or recent past cause.

Additional Information on Tense Usage

When linking clauses with conjunctions like "since" (meaning 'because'), it's important that the tenses reflect the logical relationship between the clauses.

• If the first clause describes a cause that started recently and has a present effect (using present perfect or simple past), the result clause should usually use a tense that reflects this connection to the present or recent past (often present perfect or simple past).
• Using the past perfect ("had + participle") for a result immediately following a cause described by the present perfect ("has + participle") is generally incorrect.

The segment "it had once again" should likely be "it has once again" or possibly "it became once again" depending on the desired emphasis, to align with the tense of the cause ("has started doing well").