Explanation:

- Option 1: 250 - This option is incorrect. The act does not guarantee 250 days of employment.

- Option 2: 45 - This is not the correct number of days. The act provides more than 45 days of employment.

- Option 3: 365 - This option is incorrect. While some programs may offer year-round employment, this act has a specific number.

- Option 4: 100 - The Mahatma Gandhi National Rural Employment Guarantee Act, 2005 provides 100 days of wage employment per year to every rural household. It ensures livelihood security and aims to enhance the livelihood security of people in rural areas by guaranteeing wage employment.