The best solution to address water shortages and sanitation problems would be **B. a, b, and d**.
This option encompasses:
- **Investing in infrastructure (a)** to ensure reliable water and sanitation systems.
- **Educating communities on effective hygiene practices (b)** to reduce the spread of diseases.
- **Empowering communities (d)** to manage their own water and sanitation needs, which can lead to more sustainable and locally tailored


