Can you place six X (crosses) in below board without making three in a row in any way ?

What has many teeth, but cannot bite?

Can you find the mistake in the below statement?

O_er_t_o_

Complete the missing letters of the given word.

Find the number of squares in the below picture

There are a hundred statements.

First person says: At least one of the statements is false.

Second person says: At least two of the statements is false.

Third person says: At least three of the statements are false.

Fourth person says: At least four of the statements are false.

..

..

..

Hundredth person says: At least a hundred of the statements are false.

Analysing it, how many statements do you think are false and how many are true?

Name one eight-letter word with 'kst' in the middle, 'in' the beginning, 'and' at the end.?

If a boy blows 18 bubbles,
Then pops 6 eats 7 and then
He pops 5 and blows 1.
How many are left?

The doctor advised his patient to take a tablet after every fifteen minutes. He gave him five tablets in total.

How much time will he take to have all the five tablets?

Buy me, smell me or deliver me, I do not change.

Who am I?