If all of us pull together, there must be something we can do _____.
A:improve the environment
B:to improve the environment
C:improving the environment
D:improved the environment
生物能进行呼吸,绝大多数生物需要吸入____ ,呼出____ .
下面对隋朝特点的简短总结中,哪个最为全面且符合实际( )
①具有双层膜 ②进行能量转换 ③产生氧气 ④含有DNA ⑤动、植物细胞都具有.
已知下列不等式:1ex>lnx,2tanx>sinx,32x>x2,41x>x,则在x∈0,1内上述不等式恒成立的个数为( )