उत्तर : 1. "इंदौर, मध्य प्रदेश"
व्याख्या :

1. Indore city of Madhya Pradesh has secured first place in the country in terms of cleanliness.

2. This clean air survey has been done in cities with a population of 10 lakhs.

3. Indore was declared the country's number-one clean city for the first time in 2017.