下列运算正确的是( )
A:5a2+3a2=8a4
B:a3·a4=a12
C:(a+2b)2=a2+4b2
D:-643=-4
我国的最高国家权力机关是( )
cook, on, do, live, busy, read, play, about, clean, weekend
Hello! My name is Zhang Ming. I ____ in Qingdao. I am a student. Do you want to know about my ____? I'm very happy ____the weekend. I can ____many things(事情). Usually I do my homework and ____books. Sometimes I ____the rooms and ____dinner with my mum. I often watch TV and ____ pingpong with my father. I'm ____at home. This is my weekend. What ____your weekend?
小红同学在做“研究凸透镜成像规律”的实验时,将点燃的蜡烛、凸透镜、光屏调节到如图所示的位置,光屏中心正好出现清晰的像(未画出)。下列说法中不正确的是 ( )