下列句子中，划线的词语使用正确的一项是                        (　　)

    Today is the last Saturday before Christmas. Everyone in the USA 1 shopping for presents. 2 is falling. People are walking fast. They are trying to keep3 when they move from shop to shop. In the shops children are 4 at the toys. They are talking to a man called Father Christmas. He asks, "What do you want for Christmas?"

    In the USA it is warm and beautiful in summer. The trees and fields are green then. But now it is winter and 5is white.

    At 6, small lights make the houses and buildings 7. Christmas is a beautiful 8 of a year.

    Christmas Day always begins before 9. Children wake up very early in the morning. They open the 10from their parents. Then they wake up their parents, saying "Merry Christmas."

海带 $\stackrel{①}{\to }$ 海带灰 $\stackrel{②浸泡}{\to }$ 海带灰悬浊液 $\stackrel{③}{\to }$ 含I^﹣的溶液 $\underset{H_2{O}_2}{\overset{④稀硫酸}{\to }}$ 含I₂的水溶液 $\stackrel{⑤}{\to }$ 含I₂有机溶液 $\stackrel{⑥}{\to }$ 晶体碘．

如图是a、b、c三种物质的溶解度曲线，a与c的溶解度曲线相交于P点．据图回答：

（1）P点的含义是____ ．

（2）t₁℃时30g a物质加入到50g水中不断搅拌，能形成80g溶液吗？____ （填“能”或“不能”）．

（3）t₂℃时，a、b、c三种物质的溶解度按由小到大的顺序排列的是____ （填物质序号）．