What's the only room from which no one can enter or leave

Which is Odd One Out and why?

4377

3954

9862

8454

9831

What has one letter and starts with an E?

On rolling two dices (six-sided normal dice) together, what is the probability that the first one comes up with a 2 and the second one comes up with a 5?

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.

Can you replace the question mark with the correct letter?

6 + 6 + 6 = N
7 + 7 + 7 = E
8 + 8 + 8 = R
0 + 0 + 0 = ?

What is the largest amount of money that you can possess in change and still if someone asks you for a dollar, you won't be able to give?

In the image given, you can find several triangles. Can you count them all?

I am dry when I go inside, but wet when I am pulled outside.
The longer I am inside, the stronger I get
When I am completely out, I am wet and I literally sag
Who am I?