Replace the question mark with the number below given a simple math problem.

In the figure, you can see nine stars. What you have to do is connect all of them by using just four line and without lifting your hand i.e. in a continuous flow.

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

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

Can you find the dog hidden in a group of pandas?

What is so fragile that saying its name breaks it?

If it took eight men ten hours to build a wall, how long would it take four men to build it?

A river should be crossed by a father, a mother and their two sons and two daughters.
There are some rules that should be followed while crossing the river. There can be only two people in the raft while crossing. The daughters cannot be with their father unless there is the presence of the mother. The sons cannot be with their mothers unless the father is present. Unless the guard is on the board, the criminals cannot be with any of the family members. Only the adults like the father, the guard, and the mother knows to use the raft.

How will they cross the river?

Which Number is the odd one out?

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

I am a type of room you cannot enter or leave. Raised from the ground below, I could be poisonous or a delicious treat. What am I?