What always comes into a house through the keyhole?

Which Number is the odd one out?

A) 7145
B) 2716
C) 5321
D) 4135

Replace the question mark with the correct number.

Solve below popular number sequence
314 159 265 358 979 323 846 ?

I am an eight letter word and I am a computer terminology.
The second, third and fourth letters make an animal.
The fourth, fifth, sixth, seventh and eighth letters make a weapon.
The first, second, third and fourth letters can be taken as an outcome of any exam.
The fifth, sixth, seventh and eighth letter combine to form a high end typing software.

Can you tell who am I ?

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

I don't get anymore wetter, no matter how much rain falls on me.

Two-person want to cross a river. Only one boat is present on the riverside that can carry only one person at a time.

However, they still manage to cross the river. How is it possible?

What does this rebus riddle means ?

You have $100 with you and you have to buy 100 balls with it. 100 is the exact figure and you can't go below or above the numbers and you have to use the entire $100. If there is no kind of tax applied how many of each of the following balls will you be able to buy:

Green Balls costing $6
Yellow Balls costing $3
Black Balls costing $0.10

Now, how many of each must you buy to fulfil the condition given?