What question can you never answer yes to?

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

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

There was a kingdom in which the king had no heir to take over his thrown. Even the queen was dead and he himself was on the verge of dying. He thought about it and then summoned all of the teenagers. He gave one seed each to all of them and asked them to grow the plant. He announced that the one with the most beautiful plant will become the king/queen of the empire after the death of the king.

After a month, all of them were called. The king looked at all of the plants but announced the girl with an empty pot as the queen of the empire. Why?

I sleep during the day and fly at night, but I have no feathers to aid my flight. What am I?

A man and a dog were going down the street. The man rode, yet walked. What was the dog’s name?

A chicken farmer has figured out that a hen and a half can lay an egg and a half in a day and a half. How many hens does the farmer need to produce one dozen eggs in six days?

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

Can you name some countries which do not have the alphabet 'A' in them?