The problem given below consists of a question and two statements numbered I and II. You have to decide whether the data provided in the statements are sufficient to answer the question.

Howmanysisters does Sunny have?

I. Sunny is the only son of his parents.
II. Sunny’s parents have three children

The correct option is: Statements I and II together are sufficient to answer the question.

To determine the number of sisters Sunny has, let us analyze the information provided in the statements step-by-step:

Step 1: Analyze Statement I alone
Statement I states: "Sunny is the only son of his parents."
This tells us that Sunny has no brothers, meaning all other children of his parents (if any) must be females (Sunny's sisters). However, this statement does not give the total number of children. Therefore, Statement I alone is not sufficient to find the exact number of sisters.

Step 2: Analyze Statement II alone
Statement II states: "Sunny’s parents have three children."
This tells us the size of the family but does not specify the gender of the children. Without knowing how many of these children are boys or girls, Statement II alone is not sufficient to answer the question.

Step 3: Combine Statement I and Statement II
When we combine both statements, we get a complete picture:
1. The total number of children is 3 (from Statement II).
2. Sunny is 1 of these children, and he is the only male child (from Statement I).
To find the number of remaining children, we subtract Sunny from the total:
$3-1=2$
Since Sunny is the only son, these remaining 2 children must be daughters. Thus, Sunny has exactly 2 sisters. Since we can determine the answer by using both statements together, they are sufficient.