在探究凸透镜成像规律的实验中，当烛焰、凸透镜、光屏处于如图所示的位置时，恰能在光屏上得到一个清晰的像。利用这一成像原理可以制成 A、
I really hadn't meant to yell at them. But that grey afternoon saw it just as my son and daughter were making a terrible mess on the floor in the kitchen. With a tiresome report to write, I felt bo
(本小题满分16分)已知负数a和正数b，令a1=a，b1=b，且对任意的正整数k，当≥0时,有ak+1=ak，bk+1=；当<0,有ak+1 =，bk+1 = bk．（1）求bn-an关于n的表达式； （2
We could see that he was trying to _____ his own responsibility for the delay, instead of accepting his fault. A. run over B. smooth over C. pass off D. turn down
下列判断细胞死活的方法中正确的是（ ） A. 在高倍镜下观察，若发现细胞质流动缓慢，则表明此时细胞是死细胞 B. 将植物细胞置于不同浓
内地与香港文化交流活动不断，为香港带来深厚的文化气息，这标志着两地的文化交流正在走向纵深。下列属于文化传播的有 ①内地的100名10岁
. — Where is your uncle's home? — In New York. But he___________in Boston for four years. A. has lived B. lived C. had lived D. had been living
等于 （ ）