配比时,病例和对照比例是下列哪项时统计效率最高()。
A.1:1
B.1:2
C.1:3
D.1:4
E.1:5
参考答案:D
After many years of hard work, his dream _________ at last.
A.come true
B.was come true
C.was realized
D.realized
主机箱内的存储器是内存储器。 ( )