20．
Corals（珊瑚） of the Red Sea have been a popular attraction （吸引人的东西）to divers．Due to the slow flow of water in the Red Sea，the corals there have a number of unique（独特的） characteristics，including one of a kind shapes．Here is two of them you're likely to see on a dive．
Acropora is the most common type of coral in the Red Sea and is characterized by its green or brown color，growing either in plates or branches．It grows quickly and can grow up to a meter in length in little time if left undisturbed（不被打扰）．The biggest threat to this species in the Red Sea is bleaching，which can be seen in the above photo．This beautiful coral is more commonly known as a Venus fan or a common sea fan．As its name suggests，it takes the shape of a fan and can reach from 30centimeters to 1.5meters in height．More commonly known as sun coral，it is bright yellow or orange in color．
One of the unique characteristics of Tubastrea is that this type of coral extends（伸展） its tentacles（触手） in the evenings．It is found in the deeper parts of the Red Sea．This type of coral varies in color and may be white，pink，blue，purple，or yellow．
Of course there are many to see．Fungia is generally round or oval in shape and resembles （像…一样）a mushroom．Whip coral is long and thin and looks similar to tree branches．It is most commonly yellow or orange in color，but some are purple．Whip coral is also known as sea whip．
32．Why have corals of the Red Sea been a popular attraction to divers？B
A．They are the most beautiful in the world．
B．They have a number of unique characteristics and shapes．
C．The Red Sea water flows slow．
D．The coral is well known．
33．How many kinds of corals can we see from the text？C
A.2 B.3 C.4 D.5
34．Which is Not the characteristics of Acropora？C
A．It has green or brown color．
B．It can reach from 30centimeters to 1.5meters in height．
C．It is like a mushroom．
D．It is known as a Venus fan or a common sea fan．
35．What do we know of Tubastrea？A
A．It reaches out its tentacles in the evenings．
B．It is generally round or oval in shape．
C．It is long and thin and looks similar to tree branches．
D．It is most commonly yellow or orange in color．
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