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参考解析：
刷刷题刷刷变学霸
举一反三
【多选题】滤池的承托层位于石英砂滤料下面,其主要作用有哪些( )?
A.
过滤时，防止滤料从配水系统中流失
B.
过滤时，维持过滤速度相对均衡
C.
反冲洗时，均匀分布反冲洗水
D.
反冲洗时，减缓滤层反冲洗强度。
【单选题】When stars like our Sun die, they bloat to become red giants and then eject gigantic clouds of gas and dust into space. Increasingly, however, scientists found themselves at a profound loss to explain...
A.
explain-the possible way of death of our Sun.
B.
show the two types of red giants.
C.
discuss on the way of red giants to become white dwarfs.
D.
explore the origin of life.