Explanation:

- Agra becomes the first Indian city with vacuum-based sewers in April.

- This system is a modern waste management solution.

- Vacuum sewers are efficient for areas with narrow lanes and high population density.

- Agra implemented this to manage waste more effectively near the Taj Mahal.

- Other cities mentioned:

- Jhansi: Known for its historic significance.

- Kanpur: An industrial hub but not focused on vacuum sewers.

- Gwalior: Known for its fort and palaces.

- Jaipur: The Pink City, famous for its heritage, not vacuum sewers.

Answer: Agra