Complete Question:
A. The Price Book Entry for this Product is zero.
B. The Product's ""Hidden"" field is set to True.
C. No Price Book Entry is in this Quote's currency.
D. The "Quote Line Visibility" field is set to "Never"
Answer and Explanation:
D. The "Quote Line Visibility" field is set to "Never"
Quote line visibility field is a list that determines when the options are seen after the configuration. Here, the product does not show up because the quote line visibility field is set to never. Hence, the user is unable to see the product.