笔石相
参考答案:在静水海湾或较深的深水盆地中,海底水流不畅,造成“闭塞”环境,不适于底栖生物生活,只有漂浮的笔石,死后下沉,保存为化石,形成所谓的笔石(页岩或砂岩)相。
As we all know, many Chinese words have come into English, _____ typhoon, tofu and kung fu.
A.for example
B.that is
C.such as
D.so as to
数字程控交换网实现的专用通信业务有:()等。