A man has a cat. He likes her very much. At mealtime the cat sits at the table with him. The man eats with a knife and a fork, but the cat eats from her plate. Sometimes, when she finishes her dish, her master will give her a bit of his food. He shares his meal with her. One day the cat is not at the table at mealtime.
“Ah! Where is my cat?” asks the man.
His wife says, “Can't you eat without her?”
So the meal begins without the cat. Before lunch is over, the cat rushes into the room and jumps onto the chair quickly. She has two mice in her mouth, and before anyone can stop her, she drops(扔下) one into her own plate, and the other into her master’s plate.
“Dear me!” cries the woman, “A mouse is in your plate!”
“Hush(安 静)!” says her husband. “This shows that she is a nice cat. She knows what friendship is. She wishes me to share her dinner as I often share mine with her, I am not so unhappy.”
、n个－CH2－、X个－CH3，则X的数目可能是