一块质量为100g的冰块熔化成水后，它的质量、体积和密度的说法中正确的是（）

填一填．

生物的变异是普遍存在的，下列属于可遗传变异的是  （ ）

阅读短文，下列问题

Computers are very important for the students now. For the city students, it's very easy to find a place to surf the Internet(网上冲浪). And for the village students, they can go to the Internet bar(网吧). Most of them spend more than two hours there, and some of them even spend more than eight hours there every day. They can do their homework, download(下载) some information for their homework, download music, send emails and play games.Most of them spend too much time playing games, so it's bad for their study.

端午节是我国四大传统节日之一，自古以来就有划龙舟及食粽等节日活动。直到今天，每年农历5月初，很多中国家庭都会浸糯米、洗粽叶、包粽子，其花色品种更为繁多。从馅料看，北方多包小枣，南方则有豆沙、鲜肉、八宝、火腿、蛋黄等多种馅料，各地粽子各有特色。端午食粽的风俗还传到了日本、缅甸、越南、马来西亚等国。各国包粽子的材料种类丰富，外形也不尽相同。越南人是用芭蕉叶包裹成的圆形和方形粽子，日本人连用磨碎的米粉包成的锤形粽子，朝鲜的粽子则是把鲜嫩的艾叶煮后捣碎，掺加在米粉中，再做成车轮形状，称为“车轮饼”。

韩国的端午活动丰富多彩，除吃粽子外，还要进行端午祭祀，“江陵端午祭”是韩国江陵市市民祈求丰收和安康的大型民俗活动，也是韩国端午活动的典型代表。