the answer is water, the innovation was to improve water supply, not hygiene supply.I wasn't sure about the electricity vs coal part. I wrote coal because I didn't hear electricity (must have missed) and I was hesitant as it somehow didn't make sense to see 'coal' as innovation. In hindsight, I am more inclined with electricity despite writing coal as the answer
I thought about putting hygiene but it didn't make sense in terms of the sentence. Just like you said you can't deliver hygiene, I went with water.