Always in you, Sometimes on you;

If I surround you, I can kill you.

What am I?

I cannot talk, but I always reply when spoken to. What am I?

Can you count the number of lines in the below picture?

There are 2 cops parked along a one-way street looking for traffic violations. They spot a taxi driver going in the wrong direction, yet they do nothing.

Why?

In the addition below, all digits have been replaced by letters. Equal letters represent equal digits and different letters represent different digits.
ABCABA
BBDCAA
ABEABB
ABDBAA
------- +
AAFGBDH
What does the complete addition look like in digits?

If,
29 - 1 = 30
9 - 1 = 10
14 - 1 = 15

Based on similar logic, Can you prove that the below algebraic equation is true?
11 - 1 = 10 ?

I know a nine-letter word having only one vowel.
Do you ?

What demands an answer, but asks no questions

A man stands on one side of a river, his dog on the other. The man calls his dog, who immediately crosses the river without getting wet and without using a bridge or a boat. How did the dog do it?

The more it dries, the wetter it becomes. Can you tell what it is?