Read the paragraph. Water is an important resource that people take for granted. A typical American household uses one hundred gallons of water a day. If added at the end, which sentence would complete the paragraph by connecting back to the topic?

The correct answer should be - With a little effort, people could easily protect this resource by conserving it.

These two sentences in the paragraph are talking about the importance of water, so it is only natural that the correct answer should contain information about its preservation. The other options either move away from the topic or do not show such importance of water, which is something they should do.