The question asks us to find the most appropriate option to replace the underlined phrase "is raining" in the sentence: "I will not go out if is raining."

Let's analyze the original sentence and the underlined segment. The sentence structure suggests a conditional statement, specifically describing a future action ("I will not go out") that depends on a present or expected condition ("if is raining").

The phrase "is raining" is in the present continuous tense. However, the structure "if is raining" is grammatically incorrect in standard English conditional clauses. The subject "it" is missing before "is". More importantly, for a conditional sentence where the main clause is in the future tense (using "will"), the 'if' clause typically uses the present simple tense to express a general truth or a likely future event.

This type of sentence is known as a Type 1 Conditional sentence, which follows the structure:

If + Present Simple, Will + Base Form of Verb

Let's examine the given options based on this rule:

Analysing the Options for Correct Substitution

• Option 1: raining

  This is just the present participle form of the verb. It does not form a complete clause with a subject and verb, and it is not in the correct tense for a Type 1 conditional 'if' clause.

• Option 2: It rains

  This option provides the subject "It" and the verb "rains" in the present simple tense. Substituting this into the original sentence gives: "I will not go out if it rains." This sentence perfectly fits the structure of a Type 1 conditional sentence and makes grammatical sense, expressing a future outcome dependent on a present or likely future condition (the rain).

• Option 3: will rain

  Using "will rain" in the 'if' clause ("if will rain") is generally incorrect in standard conditional sentences. The future tense (with 'will') is typically used in the main clause, not the 'if' clause, of a Type 1 conditional.

• Option 4: rained

  This option is in the past tense. Using the past tense in the 'if' clause ("if rained") would typically be part of a Type 2 conditional sentence (e.g., "If it rained, I would not go out"), which expresses a hypothetical or unlikely condition and uses "would" in the main clause. This does not match the original sentence's structure ("will not go out").

Based on the analysis, Option 2, "It rains," is the only grammatically correct and contextually appropriate substitution for the underlined segment "is raining" to form a standard Type 1 conditional sentence.

The corrected sentence becomes: "I will not go out if it rains."

Revision Table: English Conditional Sentence Types

Additional Information: Understanding the Type 1 Conditional

The Type 1 Conditional sentence is used to talk about a real or very likely situation in the future. It describes a possible condition and the probable result of that condition.

• The 'if' clause (or conditional clause) states the condition. It uses the present simple tense. Even though it refers to a future possibility (whether it will rain or not), the verb tense is present simple.
• The main clause states the result. It uses the future simple tense, typically formed with "will" + the base form of the main verb.

In the sentence "I will not go out if it rains," the condition is "if it rains" (present simple) and the result is "I will not go out" (future simple). This structure correctly expresses that the speaker's future action (not going out) is conditional on a future event (the rain) described using the present simple in the 'if' clause.