The following sentence has been split into four segments. Identify the segment that contains a grammatical error.
If I have recovered from fever, / I will start going / for swimming classes / from tomorrow.

The segment containing the grammatical error is "If I have recovered from fever".

Explanation:
In conditional sentences, when the main clause refers to a future event using the simple future tense (e.g., "I will start..."), the dependent 'if' clause expressing the condition must be in the simple present tense.

• Incorrect clause: "If I have recovered from fever" (present perfect tense)
• Correct clause: "If I recover from fever" (simple present tense)

Correct Sentence:
"If I recover from fever, I will start going for swimming classes from tomorrow."