在人体的下列细胞中,一定存在Y染色体的是( )
A:初级精母细胞
B:精细胞
C:初级卵母细胞
D:卵细胞
填空:
①+3.3的相反数是____;
②-5的相反数是____;
③____的相反数是-5.6;
④-(-8)是____的相反数;
⑤-(+6)是____的相反数.
This is my math teacher.
红海属于( )
A new iPhone costs about ________ of a second-hand one.