从某一高度相隔1秒先后释放两个相同的小球甲和乙，不计空气阻力，它们在空中下落的过程中

如图所示，重为3N的饮料盒放在水平桌面上，请作出饮料盒所受重力和支持力的示意图。

下列维生素的组合哪一项是错误的（）

A.维生素B-核黄素-口角炎

B.维生素B-钻胺素-恶性贫血

C.维生素C-抗坏血酸-坏血病

D.维生素A-视黄醛-夜盲症

E.维生素M-叶酸-动脉粥样硬化

照样子写句子。  

例：我们把敌人打败了。     

       敌人被我们打败了。

1．我把饭吃完了。

2．妈妈把窗户打开了。 

3．弟弟把地打扫干净了。

下列有关化学研究的正确说法是

A．同时改变两个变量来研究反应速率的变化，能更快得出有关规律

B．对于同一个化学反应，无论是一步完成还是分几步完成，其反应的焓变相同

C．已知2C(s)+2O₂(g)=2CO₂(g) △H₁；2C(s)+O₂(g)="2CO(g)" △H₂，则△H₁>△H₂

D．一定条件下，使用催化剂能加快反应速率并提高反应物的平衡转化率

Christmas is the anniversary of the birth of Christ, generally celebrated on December 25. It is one of the chief festivals of the Christian calendar and is (51) a social and family holiday. Christmas customs vary from (52) and among groups of different national (53) In most areas, however, homes and public places are (54) with evergreens, Christmas trees, (55) lights, and glittering ornaments. It is the busiest time of the year for merchants, and shops are filled (56) lavish displays and merchandise of all sorts. People send Christmas cards and buy gifts for their families and friends. Children look forward to (57) Santa Claus. They (58) their stockings on Christmas (59) and on Christmas morning they discover the gifts that have been left for them during the night. In the afternoon, families gather to (60) presents and to share the traditional Christmas dinner.

60().

A.transfer 

B.change 

C.transform 

D.exchange