In this passage on the Brexit referendum, choose the correct verb form to complete the sentence "A small majority of voters ________ to take Britain out of the European Union in the referendum held on June 23."

Introduction / Context:
This question tests your understanding of tense and subject verb agreement in a descriptive passage about the Brexit referendum. The writer is commenting on a relatively recent political event and wants to emphasise its continuing relevance in the present. You must decide which verb form best fits this meaning and agrees with the grammatical subject of the sentence.

Given Data / Assumptions:

• The clause to complete is "A small majority of voters ________ to take Britain out of the European Union (EU) in the referendum held on June 23."
• The subject is the noun phrase "A small majority of voters".
• The event is the voting in the referendum on a specific date in the recent past.
• The passage presents the result as a present and ongoing reality.

Concept / Approach:
Two concepts are central here:

• Subject verb agreement: In standard English, when a fraction or majority expression ("a majority", "a small minority") is the subject, the verb usually agrees with the main noun "majority", which is singular.
• Choice of tense: Present perfect is used to describe recent past actions connected to the present. Simple past or past perfect are used differently.

So we must choose a form that matches a singular subject and reflects a recent action whose effects clearly continue in the present.

Step-by-Step Solution:
Step 1: Identify the grammatical subject: "A small majority of voters". The head noun is "majority", which is singular. Step 2: For a singular subject, standard agreement requires "has", not "have". Step 3: Consider tense. Present perfect "has opted" links the past action (the referendum) to its present result (Britain is now on the path to leaving the EU). Step 4: Check "had opted": this is past perfect and would require another past event to compare with, which is not present here. Step 5: Check "will opt": future tense is incorrect because the referendum has already happened. Step 6: Check "have opted": grammatically possible with a plural subject, but the head noun is "majority", so singular agreement is preferred in formal written English.

Verification / Alternative check:
Insert each option into the sentence: "A small majority of voters has opted to take Britain out..." sounds natural and matches a commentary style article written after the event. "Have opted" conflicts with the singular head noun. "Had opted" suggests an earlier completed action relative to another past event, which the passage does not set up. "Will opt" clearly clashes with the stated date in the past.

Why Other Options Are Wrong:

• Had opted: Incorrect sequence of tenses; there is no later past reference point to justify past perfect.
• Will opt: Uses future tense even though the referendum has already taken place.
• Have opted: Treats the subject as plural, focusing on "voters" instead of "majority"; formal written usage usually follows the singular "majority".

Common Pitfalls:
Many learners are distracted by the nearby plural noun "voters" and incorrectly choose a plural verb. Others think any past event must use simple past or past perfect. In commentary writing about political decisions, present perfect is very common because it highlights that the decision still shapes current reality.

Final Answer:
The correct verb form is has opted, which agrees with the singular "majority" and expresses a recent action with ongoing consequences.