Which country gets ill every time?

Replace the question mark in the picture below.

You have two buckets - one holds exactly 5 gallons and the other 3 gallons. How can you measure 4 gallons of water into the 5 gallon bucket?

(Assume you have an unlimited supply of water and that there are no measurement markings of any kind on the buckets.)

A sundial has the fewest moving parts of any timepiece. Which has the most?

Eight of us go fourth, not back, to protect our king from an attack. What are we?

I am lying and I always lie. Tell me whether I am lying or telling the truth.

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?

There are five people. One of them shot and killed one of the other five.
We know following clues:
1. Dan ran in the NY City Marathon yesterday with one of the innocent men.
2. Mike consider being a farmer before he moved to the city.
3. Jeff is a top notch computer consultant and wants to install Ben new computer next week.
4. The murderer had his leg amputated last month.
5. Ben met Jack for the first time six months ago.
6. Jack has been in seclusion since the crime.
7. Dan used to drink heavily.
8. Ben and Jeff built their last computers together.
9. The murderer is Jack's brother. They grew up together in Seattle.

Consider yourself to be a famous detective "Sherlock Homles", Can you find the killer?

I have an eye but still cannot see.

Who am I?

One is to three as three is to five and five is to four and four is the magic number.
What is the pattern?