Which one are best? It is time to bed. Is Sandy birthday in May? 哪里错了

1、Which one are best?
Which one is the best?
哪一个是最好的?
(Which one 是单数,所以用is,best是*前面需加the)
2、It is time to bed.
it is time to go to bed(睡觉时间到了,需加go to）
睡觉时间到了
3、Is Sandy birthday in May?
Is Sandy's birthday in May?(仙蒂的生日,的需用名词所有格,加's,不然就成了仙蒂生日）
仙蒂的生日在五月吗?
希望能帮到你.