A:33
B:4
C:43
D:42-3
Sam: Come on, it's time for school.
Mike: What class do you have today?
Sam: I have math, music and PE. How about you?
Mike: I have English, art and music.
Sam: I like English. What about you?
Mike: I like music.
选择正确的答案填在括号里。
上生物实验课时,小刚发现他所用的显微镜是目镜、物镜上分别标有5倍和10倍字样,则他所用显微镜的放大倍数为( )