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    Welcome to Class 4, Grade 7. This is our classroom. There are twenty boys and twenty -four girls in the classroom. The teacher's desk is in the front of the classroom. There is a big blackboard on the front wall and a small blackboard on the back wall. There are two maps on the wall. One is a map of China and the other is a map of the world．There are some photos on the wall. There are some flowers by the windows. Our classroom is very beautiful.

读下列句子，用划线的词语写句子。

在外边做事的人，除非万不得已，必定赶回家来吃团圆饭。

若向量$\overrightarrow{a}$=(1,1)，$\overrightarrow{b}$=(2，5)，$\overrightarrow{c}$=(3,)满足条件(8$\overrightarrow{a}$—$\overrightarrow{b}$)·$\overrightarrow{c}$=30，则x= (  )

下列属于藻类植物的是（  ）