What does this rebus mean?

O
N
C
E
TIME

Why do Chinese men eat more rice than Japanese men do ?

I had an infinite supply of water and 5 litres and 3 litres jars.

How would you measure exactly 4 litres in the least number of steps?

Can you count the number of seconds in a year?

Clue: You need to bother about calculation.

Can you find out the missing number in the grid?

Can you spot what's wrong with the following sentence?

PETER WAS ANGRY AT
HIMSELF BECAUSE HE
ACCIDENTALLY LEFT THE
THE KEYS TO HIS CAR
AT HIS FRIEND'S HOUSE.

An infinite number of mathematicians are standing behind a bar. The first asks the barman for half a pint of beer, the second for a quarter pint, the third an eighth, and so on. How many pints of beer will the barman need to fulfill all mathematicians' wishes?

The more of this there is, the less you see. What is it?

Get total of 120 by using five zeros 0,0,0,0,0 and any one mathematical operator.
Do you ?

It is a nine-letter word.
The exact opposite of the phrase "friendly and outgoing"
It contains the word "over".
It starts will a vowel.

What is it?