阅读理解. A new study in West Africa shows how farm irrigation systems powered by the sun can produce more food and money for villagers.The study in Benin found that solarpowered pumps are effective in supplying water,especially during the long dry season. SubSaharan Africa is the part of the world with the least food security.The United Nations Food and Agriculture Organization estimates that more than one billion of the world's people faced hunger last year.Around 265 million of them live south of the Sahara Desert.Lack of rainfall is one of their main causes of food shortages. Jennifer Burney from Stanford University in California led the study.The research team helped build three solarpowered drip irrigation (滴灌) systems in northern Benin.Between 30 and 35 women used each system to pump water from the ground or a stream.Each woman was responsible for farming her own 120 square meters of land.They also farmed other land collectively. The solarpowered irrigation systems produced an average of nearly two tons of vegetables per month.During the first year,the women kept a monthly average of almost nine kilograms of vegetables for home use.They sold the surplus produce at local markets.The earnings greatly increased their ability to buy food during the dry season which can last six to nine months.People in the two villages with the systems were able to eat three to five more servings of vegetables per day.But making the surplus available at markets also had a wider effect. The study compared the villages with two others where women farmed with traditional methods like carrying water in buckets.The amount of vegetables eaten in those villages also increased,though not as much.The researchers note that only four percent of the cropland in SubSaharan Africa is irrigated.Using solar power to pump water has higher costs at first.But the study says it can be more economical in the long term than using fuels like gasoline,diesel or kerosene.And solar power is environmentally friendly. 1．Food security in SubSaharan Africa is insufficient mainly because of________. A．lack of rainfall B．limitation of farmland C．a small crop variety D．little sunlight 2．From the third paragraph we know that________. A．water is wasted by using the system B．the farmers irrigate the land together C．all farmers use irrigation systems in northern Benin D．the solarpowered systems take up more manpower 3．The underlined word 'surplus' in the 4th paragraph most probably means________. A．special B．unnecessary C．extra D．abandoned 4．Using solar power to pump water has advantages EXCEPT that________. A．solar energy has higher cost at first B．solar power helps to protect environment C．solar power helps farmers increase earnings D．solar energy can be more economical in the long run 5．What can be the best title for the text? A．Manpower affects rainfall in Africa B．Irrigation by carrying water in buckets C．Solarpowered pumps aid African farmers D．Vegetable supply increased in African villages