Answer:
Rezwan's floating classrooms educate children and improve lives.
Step-by-step explanation:
The central idea (also called the main or key idea) of a text is the main point the author is making. When we're looking for the central idea, we are actually looking for the sentence that tells us what the text is about.
Supporting ideas provide us with additional information about the central idea. Here, you were given six supporting ideas - three as a part of the question and another three as incorrect options.
We can see that the first three supporting ideas are about floating classrooms - what they are, how they work, and what they do. All given options, except for the fourth one, are similar - they tell us more about these classrooms and why they are important.
The fourth option simply introduces Rezwan's floating classrooms and tells us that they are important. That is the central idea, and the rest of the ideas tell us more about it.