若是任意非零常数,对于函数有以下5个命题:①是的周期函数的充要条件是;②是的周期函数的充要条件是; ③若是奇函数且是的周期函数,则的图形关于直线 对称;④若关于直线对称,且,则是奇函数;⑤若关于点对称,关于直线对称,则是的周期函数.其中正确命题的序号为 .
Every coin has two sides. My bad luck has (unexpected) turned into a good thing.
As a traditional festival, Mid﹣Autumn Day is c in China every year.
Under the leadership of Chairman Xi, China will become much stronger w doubt.
As a mountain climber, Aron is used to (take)risks.
The weather report says it will be (sun) in the following two days.