A、Mobile technology experts. B、Ecosystem activists. C、Mothers and their children. D、Private charity workers. A短文开头说，邀请参加会议的人员涉及非

Different groups around the world are working to expand the uses for mobile technology in health care. Patricia Mechael is executive director of an organization called the mHealth Alliance. She says a lot of work is being done to use mobile technology for mother and child health. More than 4, 000 people from 50 countries have been meeting near Washington this week. The meeting is the fourth annual mHealth Summit. It brings together experts from what the organizers call the mHealth ecosystem.(20)This includes nongovernmental organizations, governments and the technology industry.
    In 2011 Secretary of State Hillary Clinton launched a public/private partnership called the Mobile Alliance for Maternal Action, or MAMA. Kirsten Gagnaire is the global director of MAMA.(21)She says the MAMA program sends messages to mobile phones to educate women about their health. She says health messages may also be sent to a pregnant woman’s husband and mother-in-law, for example. That way they too can understand what needs to be done. Patricia Mechael of the mHealth Alliance says messages can be text or voicemail. Even simple text messages can be important sources of information to people without Internet access.(22)And Kirsten Gagnaire of the Mobile Alliance for Maternal Health says even online users may not understand all the information available. You have to be able to read through thousands of entries that come back to you on Google, for example, and then figure out what that information means to you. And that’s not something that someone in a poor, illiterate or semi-literate kind of situation can do.
20. Who are invited to attend the mHealth Summit?
21. What kind of messages do MAMA send via mobile phone?
22. What advantage do phone messages have over Internet?