O_er_t_o_

Complete the missing letters of the given word.

What month of the year has 28 days?

If eleven plus two equals one, what does nine plus five equal?

If an electric train is travelling south, then which way is the smoke going?

How can you take 2 from 5 and leave 4?

I came first on earth but second on the heaven.
I also came twice in a week but found just once in a year.
I stay away from months but you can find me in February.

What am I?

Known by all without exception, Forever here, for your protection, Sometimes strong, sometimes weak, Right after the night I come - hot and chic. And while millions of miles away, I always get to you, I find my way. No life around could do without me, Can you guess what I might be?

I know there are two methods by using three time the same number with a plus(+) operator , you can make sum as 60.

One of them is 20+20+20.

whats the other way ?

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

I am white when I am dirty, and black when I am clean. What am I?