The answer to each of the following questions is a single digit integer ranging from 0 to 9. It the correct answers to the questions numbers A, B, C and S (say ) are 4, 0,9 and 2 respectively thent the correct darkening of bubbles should be us shown on the side :
How many of the following elements are s- block elements
`Rb, A1 ,B , K ,S, Cd, Zn , Th, Sr .`

Explanation

To determine how many of the given elements are s-block elements, we need to identify which of the listed elements belong to the s-block of the periodic table. The s-block includes the elements in Group 1 (alkali metals) and Group 2 (alkaline earth metals).

### Step-by-Step Solution:

1. **List the Given Elements**:
The elements provided are Rb (Rubidium), Al (Aluminum), B (Boron), K (Potassium), S (Sulfur), Cd (Cadmium), Zn (Zinc), Th (Thorium), Sr (Strontium).

2. **Identify the s-block Elements**:
- **Group 1 (Alkali Metals)**:
- Rb (Rubidium) - Yes, it is an s-block element.
- K (Potassium) - Yes, it is an s-block element.
- **Group 2 (Alkaline Earth Metals)**:
- Sr (Strontium) - Yes, it is an s-block element.
- **Other Elements**:
- Al (Aluminum) - No, it is a p-block element.
- B (Boron) - No, it is a p-block element.
- S (Sulfur) - No, it is a p-block element.
- Cd (Cadmium) - No, it is a d-block element.
- Zn (Zinc) - No, it is a d-block element.
- Th (Thorium) - No, it is an f-block element.

3. **Count the s-block Elements**:
From the analysis, the s-block elements identified are:
- Rb (Rubidium)
- K (Potassium)
- Sr (Strontium)

Therefore, there are a total of **3 s-block elements**.

### Final Answer:
The number of s-block elements among the given elements is **3**.

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