在学习物理的过程中，经常需要估测，以下估测较为符合实际的是（　　）

①***是中国特色社会主义事业的领导核心

②我国实行共产党领导的多党合作和政治协商制度

③人大代表是国家权力机关的组成人员，代表人民行使决定权

④人民政协是协商民主的重要渠道，履行参政议政的国家职能

在天平两端各放等质量的两个锥形瓶（瓶口用单孔塞和导管连接起来，气球中装有等质量的大理石），如图所示．左盘锥形瓶中盛有M 克水，右盘锥形瓶中盛有M 克稀盐酸，天平平衡．

（1）实验开始时，将气球中的大理石倒入锥形瓶中，观察到的现象是____ ，天平的指针____ （填“偏左”“偏右”“在标尺中央”下同），原因是____ ．

（2）待上述实验的反应完成后，将锥形瓶瓶口上的单孔塞、导管和气球去掉，天平的指针____ ；原因是____ ．

阅读短文，从方框中选择适当的词并用其正确的形式填空，使短文通顺、意思完整。请每空限填一词，每词限用一次。方框中有两项多余的。

Are you still doing the V for victory sign? It's out. The latest popular hand gesture（手势）is putting both of your hands and put them together to make a heart—shape. It is  ____ “hand heart”.

 Many young pop    ____  in the US have done the move in recent photos. “The‘hand heart’gesture means something    ____   'I love you' and 'thank you’, ”said Taylor Swift,the country singer.  “You can send a sweet，simple message without ____  a word.”
 Swift often does it at her concerts. And she is believed to be the first to   ____  it popular.
 Last month，Justin Bieber and____ uperstar friends did the “ hand heart” and put the photos online.They did it to help out three kids whose parents were killed in a car accident.

“It used to take much  ____  for nonverbal（非语言的）culture to move. But now ,It moves faster____ we have smart phones and the Internet.
In the Republic of Korea, the “hand heart “ has been  ____  for a long time, but in a different  ____  . People there put their hands above their heads and making a bigger heart shape with their arms. It means: “I love you.”