Platypus and koala are also rare animals.They are ________

Kangaroo,Koala,Platypus,Crocodile,Wombat,Emu,big,bigger,small,smaller,fast,faster,slow,slower的音标

sat关于定于从句等的修饰对象
1.the evolution of the platypus,originally called the watermole,is still a mystery to the biologist.
originally called the watermole为什么指代 Platypus
2.the north american continet was first colonized by people from siberia,who crossed the new sunken land bridge between siveria and alaska about 15000years ago.
who为什么指代people
3.The grooved and barbed spears of the box jellyfish,each trailed by a poison thread,is realeased when the animal is threatened.(from IE)
each trailed 为什么指代spears