Yesterday was my 18th birthday. As Father and Mother thought it____ (be) a big occasion for me, they suggested I ____ (held) a birthday party at home to celebrate it. For several days they had been busy ____ (prepare) for this. By 4 o'clock I was pleased to see all my friends had come ____ a lot of beautiful presents.

    We spent a wonderful night together, ____ (happy) talking and eating. One of ____ most exciting moment was when Mother put a big birthday cake on the table and all my friends began to sing Happy Birthday. Seeing the 18 candles burning, I couldn't keep back my ____ (tear). Without Mother and Father's love, I would not lead such a happy life now. Mother asked me to make a wish before I blew out all the candles. After that, everyone enjoyed the sweet birthday cake and shared my happiness.

    I am eighteen years old now, ____ means I've become an adult and have ____ (many) responsibilities. I'll do my best to return my parents' love and live up to ____ (they) expectations.

 世博会上所使用的饭盒、胸卡、证件等都用可完全降解的“玉米塑料”制成，制作的第一步是将玉米发酵制得乳酸(C₃H₆O₃)。试列式计算：
（1）乳酸的相对分子质量。
（2）多少克乳酸与88克二氧化碳中所含碳元素的质量相等？

在新中国建立之初进行的抗美援朝和土地改革运动的共同作用是

黄河流域原始农耕时代的居民是（   ）