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Complete the missing letters of the given word.

There are three boxes of different sizes with three cupcakes inside each of the boxes in Christina's kitchen. At night her daughter wakes up and goes to the kitchen. She opens a box and eats all three cakes.

But in the morning Christina finds out that each box still had three cupcakes. How?

How many letters are in the alphabet?

Next Number in the Series,

5, 16, 49, 104, ?

When I go in I might cause pain. I cause you to spit and ask you not to swallow. I can fill your hole. What am I?

Count the number of triangles in the picture below:

Can you figure out the logic I used to decide the order of the following words:
gun, shoe, spree, door, hive, kicks, heaven, gate, line, den

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.

What has one eye, but can’t see?

Count the number of lines in the image below ?