他们围着老师的椅子站成半圆形回答问题。They stood in a semi-circle round the teacher's chair and answered questions.摆成半圆形的椅子a semicircle of chairs这个村庄是由半圆形的茅舍组成的.The village was formed of semicircle huts....
他们群集在老师的周围.They trooped around the teacher.囚犯群集在围墙里.The prisoners horded together in the compound.特定的群集度是多数植物特有的特征.A certain sociability degree is a specific character of most plants....
我们在威斯敏斯特教堂看到的是一种经年不变的古旧仪式。What we see at Westminster is a tired old ritual.然而，我们脚下的地面却似乎是坚实而恒久不变的。The ground beneath us, however, appears solid and unchanging.这是持久不变的.It is unchangeable and permanent....
牙斑如果不清除就会导致牙齿蛀蚀和牙龈疾病。When not removed, plaque causes tooth decay and gum disease.牙齿和牙龈之间会滋生牙斑。Deposits of plaque build up between the tooth and the gum.需刷牙以去除牙斑.It is necessary to remove plaque by brushing one's tee...