Explanation:
Before explaining the correct answer, let's understand the given sentence.

The sentence states that "They will read the report fully before they ___." Here, we need to determine the correct verb form that should be used after "before they."

Understanding the verb tense:
The verb tense used in the sentence is "will read," which is in the future tense. This indicates that the action of reading the report will happen in the future.

Understanding the verb form:
The verb form that should be used after "before they" in this context should be in the base form (infinitive) because the action of reading the report comes before the action of voting. The base form of the verb is the simplest form of the verb without any tense markers or additional suffixes.

Identifying the correct option:
Let's analyze the given options to determine the correct one:

- Option 'a)would vote': This option uses the conditional form 'would vote,' which indicates a hypothetical or uncertain action. However, the sentence does not suggest any condition or uncertainty, so this option is incorrect.
- Option 'b)will vote': This option uses the future tense 'will vote,' which does not match with the context. The action of voting comes after reading the report, so using the future tense here would imply that they have already read the report, which is not the intended meaning. Therefore, this option is incorrect.
- Option 'c)vote': This option uses the base form 'vote,' which is the correct verb form in this context. It indicates that the action of voting comes after reading the report, aligning with the given sentence. Therefore, this option is correct.
- Option 'd)voted': This option uses the past tense 'voted,' which does not match with the future tense used in the sentence. Therefore, this option is incorrect.

Conclusion:
Based on the analysis, the correct answer is option 'c)vote' because it uses the base form of the verb, which aligns with the future tense used in the sentence.