In this task, you're given an article and an answer. Your task is to generate the fill-in-the-blank question for this answer based on the given article. The blanks are always at the end of the question, and can be filled with more than one word or phrase.

Article: The story happened during the Second World War. An old man lived in a small town of Germany. He had three sons and they all worked in the same factory where he had worked. After the war had begun, his sons were all made to join the army one after another and they all died in the fights. The old man was very sad. He didn't have enough food and was often hungry. And nobody helped him and he didn't know how to go on living. It was a very cold winter night. The old man couldn't go to sleep. He had been hungry for two days and it was so cold in his room that ice could be seen. He had to get up and began to run in the room until he lay down on the floor. The next morning he had to beg from door to door. He had been to a lot of cities and knew a lot. Once he came to a village, but the villagers were all poor and couldn't give him anything. He was too hungry to go to another village. He thought hard and found a way. He came to a police station and called out, "Hitler is a foolish pig!" Out came an old policeman at once. He took the old man into a room, gave him some bread and a cup of tea. Then he said, "Don't say so in our village, sir!" "I'm sorry, sir," said the old man. "I don't know it's Hitler's hometown." "No, no, sir," the policeman said in a hurry. "It's pigs' hometown!"
Answer: they had to do so
The old man's sons joined the army because _ .

Article: When we see well, we do not think about our eyes very often. It is only when we cannot see perfectly that we realize how important our eyes are. People who are near-sighted can only see things that are very close to their eyes. Everything else seems blurry (unclear). Many people who do a lot of work, such as writing, reading and sewing become near--sighted. People who are far-sighted _ from just the opposite problem. They can see things that are far away, but they have difficulty in reading a book unless they hold it at arm's length. If they want to do much reading, they must get glasses, too. Other people do not see clearly because their eyes are not exactly the right shape. They have what is called astigmatism . This, too, can be corrected by glasses. Some people's eyes become cloudy because of cataracts . Long ago these people often became blind. Now, however, it is possible to operate on the cataracts and remove them. Having two good eyes is important for judging distances. Each eye sees things from a slightly different angle. To prove this to yourself, look at an object out of one eye; then look at the same object out of your other eye. You will find the object's relation to the background and other things around it has changed. The difference between these two different eye views helps us to judge how far away an object is. People who have only one eye cannot judge distance as people with two eyes.
Answer: only when we realize how important our eyes are
We should take good care of our eyes _ .

Article: One of the major functions of an iPhone is, of course, to play music. The iTunes app has been designed in such a way as to take advantage of the iPhone's touch screen. But what if you want to listen to music that isn't in your iTunes library, or you want to discover new music without sitting in front of computer? There are plenty of ways to access music, but not everyone knows what options are available. Either that, or there are so many options that going through all of them is tiring. For these reasons, here we offer a few convenient ways of listening to music on your iPhone without using iTunes. Stream some radio (Tuneln Radio) Tunnel Radio provides a quick and easy way to listen thousands of Internet radio stations on your Apple products. In addition to local radio stations, this app compiles more than 40 000 radio stations from around the country. What makes the app special is that it allows you to pause and rewind live radio----pause your station to take a phone call or rewind to replay a favorite song. You can also browse by genre of location, and the app includes plenty of talks, news, sports and weather stations in addition to music. From desktop to smartphone (QQ Music) QQ Music seems like obvious choice, and it is. It's a streaming service based on the Tencent technology that is already wildly popular on the Internet and now also offers a (free) app. Through this app you can listen to existing playlists or create new ones based on the patterns of music you like. It works amazingly well and everything can be saved to your QQ account for access from a computer. What was that song? (Shazam) Shazam is an innovative and free app that cures your"what was that song?"problem. It happens to all of us : we hear a song (on TV or in a store ), love it, know we have heard it before but just can't remember what it is called . With Shazam you don't need to. Just hold your iPhone up and through its microphone, Shazam will identify the album, artist and song title for you. You can then either purchase the song in iTunes or search it on other apps for streaming. How cool is that?
Answer: iPhones
All of the options are strongly recommended to the users of _ .