Final answer:
The total number of red wine bottles the friend has is the sum of the individual wines: 9 bottles of Zinfandel plus 11 bottles of Merlot plus 13 bottles of Cabernet, which equals 33 bottles in total.
Step-by-step explanation:
To calculate the total number of red wine bottles the student's friend has, we simply add the number of each type of wine bottle together. The friend has 9 bottles of Zinfandel, 11 bottles of Merlot, and 13 bottles of Cabernet.
9 bottles of Zinfandel + 11 bottles of Merlot + 13 bottles of Cabernet = 33 bottles of red wine in total.
Therefore, the answer is 4) 33.