Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.

Context: The U.S. Census for 2010 reported 332,199 households in Indianapolis, with an average household size of 2.42 and an average family size of 3.08. Of the total households, 59.3% were family households, with 28.2% of these including the familys own children under the age of 18; 36.5% were husband-wife families; 17.2% had a female householder (with no husband present) and 5.6% had a male householder (with no wife present). The remaining 40.7% were non-family households. , 32% of the non-family households included individuals living alone, 8.3% of these households included individuals age 65 years of age or older.
Question: Which group from the census is smaller: non-family households or husband-wife families?
husband-wife families

Context: Many people have problems with their vision, or ability to see. Often, the problem is due to the shape of the eyes and how they focus light. Two of the most common vision problems are nearsightedness and farsightedness, which you can read about below. You may even have one of these vision problems yourself. Usually, the problems can be corrected with contact lenses or lenses in eyeglasses. In many people, they can also be corrected with laser surgery, which reshapes the outer layer of the eye. Click image to the left or use the URL below. URL: Nearsightedness, or myopia, is the condition in which nearby objects are seen clearly, but distant objects appear blurry. The Figure 1.1 shows how it occurs. The eyeball is longer (from front to back) than normal. This causes images to be focused in front of the retina instead of on the retina. Myopia can be corrected with concave lenses. The lenses focus images farther back in the eye, so they fall on the retina instead of in front of it. Q: Sometimes squinting the eyes can help someone see more clearly. Why do you think this works? A: Squinting may improve focus by slightly changing the shape of the eyes. When you squint, you tighten muscles around the eyes, putting pressure on the eyeballs. Farsightedness, or hyperopia, is the condition in which distant objects are seen clearly, but nearby objects appear blurry. It occurs when the eyeball is shorter than normal (see Figure 1.2). This causes images to be focused in a spot that would fall behind the retina (if light could pass through the retina). Hyperopia can be corrected with convex lenses. The lenses focus images farther forward in the eye, so they fall on the retina instead of behind it. Q: Joey has hyperopia. When is he more likely to need his glasses: when he reads a book or when he watches TV? A: With hyperopia, Joey is farsighted. He can probably see the TV more clearly than the words in a book because the TV is farther away. Therefore, he is more likely to need his glasses when he reads than when he watches TV.
Question: in hyperopia, the eyeball is
shorter than normal.

Context: It's time to be water efficient! As populations increase across Australia and the rest of the world, demand for water will also increase. If we don't reduce each individual's demand for water (both directly and through embodied water) the water situation will become dire. It is obvious that we cannot increase demands for water much more without detrimental effects to the environment, society and the economy. It's all too easy to blame someone else for the water situation -"if 70% of water is used for agriculture then that's what we should target" - but it's not that easy. We all depend on the food and resources that agriculture provides, and while there are definitely opportunities to increase water efficiency on the farm, the solution will take more than that. We each share responsibility for the sustainable management of our water resources, which means using less water at home, in the workplace, at school, on holidays, on the farm, ... everyone, everywhere, every time. It's time to become water efficient! This involves reassessing our relationship with water, and learning to use it more sparingly. On the most basic level, it requires a behavioural change, and assigning a value to water that truly reflects its worth. We can also unlock economic benefits of being water efficient. There are many real world examples given in the case studies on this site. Everybody has a responsibility to save water, if future generations are to enjoy a similar standard of living to the one we enjoy now. In fact, many of the impacts associated with water use are likely to have an effect on our own lives! www.savewater.com.au has been designed to help you respond to the challenge to become water efficient. It acts as a central repository for relevant information and further advice, so that you can actually achieve significant savings. It also showcases those companies with products that will assist you in your goal.
Question: What is the main idea of this passage?
it's time to be water efficient.