Why do people go to bed?

Cristina was born in 1888. She just had her 30th birthday today how did that happen?

There is a river to cross using a river raft and there are eight people (father, mother, policeman, thief, 2 daughters and 2 sons). No one knows to operate the raft except the adults and also excluding the thief. Only two people can go in the raft at a time. The raft should keep coming back and forth in order to pick and drop the people.
Rules to be followed:
Father: the father cannot stay in the raft or outside the raft without the presence of the mother.
Mother: the mother cannot stay in the raft or outside the rat without the presence of the father.
Thief: the thief is not allowed to stay with any of the family members unless there is a policeman.
Policeman: the policeman can travel with anyone.
2 sons and 2 daughters: they are not allowed to travel in the raft without the presence of an adult. They cannot either travel in the presence of only thieves without the policeman. The sons cannot be with their mothers without their father's supervision. The daughters are not allowed to be there with their fathers without the supervision of their mothers. But the daughters and the sons can be left unsupervised (as long as the other rules are applied).
What is the sequence that the people should follow in order to cross the river through the raft keeping in mind all the rules?
The rules are applicable not only in the raft but also outside the raft.

In two decks of cards, what is the least amount of cards you must take to be *guaranteed* at least one four-of-a-kind?

What country can make you shiver?

There are two candles. Both will only burn exactly for an hour. How will you use these two candles to measure forty-five minutes?

You have to put a letter on the following to make it a meaningful word. The only challenge is that you can't use 'E'.

S E Q U E N C _

Two-person want to cross a river. Only one boat is present on the riverside that can carry only one person at a time.

However, they still manage to cross the river. How is it possible?

How many letters are in the alphabet?

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?