What is the Surname of Barbie Doll?

What do you think with the below Picture ?

Which word does the below Plexor means ?

A father's child, a mother's child, yet no one's son.

Who am I?

Christina, Allison and Lena are 3 daughters of John a well-known Mathematician, When I asked John the age of their daughters. He replied "The current age of her daughters is prime. Also, the difference between their ages is also prime."

How old are the daughters?

Using the clues below, what four numbers am I thinking of?

The sum of all the numbers is 31.
One number is odd.
The highest number minus the lowest number is 7.
If you subtract the middle two numbers, it equals two.
There are no duplicate numbers.

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

Can you Find and name the hidden bird in the picture below ?

The cream is heavier than Milk. True or False?

As shown in the image, the nine Dogs are square fenced. By constructing just two square fences can you make sure that two Dogs cannot meet each other without crossing the fence?