The correct option to fill the gap in the sentence "He must be a good student because he is a .... reader" is C. voracious. Step-by-Step Explanation:

1. Understanding the Sentence Context:
2. The sentence suggests that the person being described is a good student, and this is supported by their reading habits. Therefore, the word that fills the gap should convey a positive quality about the reader.
3. Analyzing the Options:
4. A. romanesque: This term generally refers to a style of architecture or art that is reminiscent of the Romanesque period. It does not relate to reading habits or imply anything about being a good student. Thus, it is not a suitable choice.
5. B. veracious: This word means truthful or honest. While being truthful is a good quality, it does not specifically relate to reading or imply that someone is a good student. Therefore, it does not fit the context of the sentence.
6. C. voracious: This term means having a very eager approach to an activity, especially eating or reading. A "voracious reader" is someone who reads a lot and with great enthusiasm. This quality is directly related to being a good student, as it suggests a strong desire to learn and absorb information. Hence, this is the correct choice.
7. D. mendacious: This word means dishonest or lying. A mendacious reader would imply someone who is not truthful, which is a negative trait and contradicts the idea of being a good student. Therefore, this option is also incorrect.
8. Why C is the Best Choice:
9. The word "voracious" directly correlates with the idea of being a good student. A voracious reader is likely to engage deeply with texts, seek out knowledge, and develop a broad understanding of various subjects. This eagerness to read and learn is a hallmark of successful students.
10. Common Pitfalls:
11. Students might confuse "veracious" with "voracious" due to their similar sounds. However, understanding the meanings is crucial. Remember that "veracious" relates to truthfulness, while "voracious" relates to eagerness and enthusiasm, especially in the context of reading.

Revision Summary:

• The correct answer is C. voracious.
• "Voracious" means eager and enthusiastic, especially about reading.
• "Veracious" means truthful, which does not relate to reading habits.
• "Mendacious" means dishonest, and "romanesque" refers to a style of art, neither of which fit the context of being a good student.

By understanding the meanings of these words and their relevance to the context, you can effectively choose the appropriate option in similar questions.