2 years old.
Cow: "Mooooove over"
Sheep: "Naaaaaaa."
or
Three. One to climb the ladder while the second kicks the ladder out from under her. And the third to say, "I knew that was too high for you dear."
or
Because it's between ac.
or
Fifty — one to screw in the bulb and 49 to guard him/her.
or
Because they are black and white.
or