Explanation:

- To find the longest pole that can fit in the hall, calculate the space's diagonal.

- The hall's dimensions are 60 feet (length), 30 feet (breadth), and 20 feet (height).

- Use the formula for the space diagonal in a rectangular box:

$$

\text{Diagonal} = \sqrt{\text{length}^2 + \text{breadth}^2 + \text{height}^2}

$$

- Substitute the hall dimensions into the formula:

$$

\text{Diagonal} = \sqrt{60^2 + 30^2 + 20^2} = \sqrt{3600 + 900 + 400} = \sqrt{4900} = 70 \text{ feet}

$$

- Option 2: 70 feet is the correct answer.