What is so fragile that saying its name breaks it?

Who always enjoys poor health?

Which statement is true out of the following?
One statement here is false.
Two statements here are false.
Three statements here are false.

Why Aeroplane windows are round?

I have one of the three numbers: 1, 2, or 3 in my mind. I speak only truth. You can ask me just one question for which I will only reply in yes or no or don't know. What question will you ask from me so that you are able to know the number?

A bag contains 64 balls of eight different colours. There are eight of each colour (including red). What is the least number you would have to pick, without looking, to be sure of selecting 3 red balls?

Can you find out which triangle will have a bigger area among the following?
1. A triangle with sides 300, 400 and 500
2. A triangle with sides 300, 400 and 700

I know a ten-letter word in the English language which can be typed using only the top rows of the computer keyboard.

Do you know of a place where the wind blows south and then suddenly shifts direction towards the north?

What English word has three consecutive double letters?