The following sentence has been split into four segments. Identify the segment that contains a grammatical error.
My older brother, / which you’ll / meet later, / is a dentist.

To identify the segment containing a grammatical error, let us analyze the sentence step-by-step:

1. Analyze the structure of the sentence:
The sentence is: "My older brother, / which you’ll / meet later, / is a dentist."
Here, "My older brother" is the subject, and the clause "which you'll meet later" is a relative clause providing additional information about the subject.

2. Examine the relative pronoun:
In English grammar, relative pronouns must agree with the noun (antecedent) they refer to:
- "Which" is used to refer to animals, objects, or inanimate things.
- "Who" or "whom" is used to refer to people.
Since the antecedent in this sentence is "My older brother" (a person), using the relative pronoun "which" is grammatically incorrect. Instead, the objective relative pronoun "whom" (or "who" in informal usage) should be used because it acts as the object of the verb "meet" (you will meet him).

3. Correction:
The grammatically correct sentence should be:
"My older brother, whom you’ll meet later, is a dentist."

Therefore, the segment containing the grammatical error is "which you’ll".