Jack and Anna are good friends. They are Chinese. Jack likes sports very much. He can play volleyball , basketball and football . Anna likes music very much . She can't play ball games. But they both like playing on computers . They like eggs , bread and milk for breakfast . For lunch , Anna likes eating vegetables and fruit , but Jack likes chicken and fish . They both like hamburgers .But they don't like ice cream or rice.

把一刚摘下的果树枝装在小瓶中，如图所示，用弹簧秤测得重为50克，光照6小时后，测得重为45克，重量减少的主要原因是（    ）

量子通讯卫星是一种传输高效的通信卫星，彻底杜绝间谍窃听及破解的保密通信技术，具有很强的抗衡外国的网络攻击与防御能力，2016年8月16日，我国首颗量子卫星（“墨子号”）成功升空，运行在高度约500km的圆形轨道上，下列说法正确的是（   ）

It's the ____ ____.