已知A（2,3），B（1,4），C（6,9），D（10,11），证明：四边形ABCD是直角梯形。 (12分)
最少用4个同样的小正方体才可以拼成一个大正方体。[ ]
In 2001 the Chinese people were always in high spirits, for pieces of exciting news came to China
________.[ ]
A. step by step
B. one by one
C. little by little
D. one after another
