1949年10月1日，中华人民共和国的成立标志着 _____。
I have been studying here for four years, by next summer I ________.
我国农业社会主义改造基本完成的标志是 ______。
Others argue that since the earth has endured a long string of ice ages in the last two millionto three million years, any warming is ________ to be temporary.
Hot metal ________ as it grows cooler.
