What is the word or phrase?

What is Luis Suarez's (Soccer Player) favorite tea?

An express train takes 3 seconds to enter the tunnel which is 1 km long.
If it is travelling at 120 km an hour, how long will it take to pass completely through the tunnel?

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

I come in different shapes and sizes.
Parts of me are curved, other parts are straight.
You can put me anywhere you like,
but there is only one right place for me.
What am I?

Why do we preferably have round manhole covers and not square ones?

You are in a room that has three switches and a closed door. The switches control three light bulbs on the other side of the door. Once you open the door, you may never touch the switches again. How can you definitively tell which switch is connected to each of the light bulbs?

Solve the below puzzle by replacing the question mark with the correct number.

3 6 12

4 8 16

5 10 ?

What is the largest number you can write with just 3 digits?

You can see it everyday, But cannot touch it at will. What is it?