This is _____ orange. _______ orange is on the table.

A. a, The　　　　 B. an, The　　　　 C. an, An　　D. the, An

"Tammy! Come here, please! Mother needs your help in the kitchen." Her father called out to her.
Tammy was in her room, getting ready to do her homework. "Yes, Daddy!" she replied. "I'll be right there."
She hurried out of her bedroom and down the hallway. She was only nine years old. Her elder sister, Ella, had just moved away to go to a performing arts high school in another city. Her brother, Harry, was in middle school and always got home late. With Ella leaving home, Tammy was expected to do a lot more than she had ever done before, especially now, because her mother was ill.
Her father was in the kitchen. "Tammy, I know you usually do your homework right now, but with things being different, we all have to change a little bit. I'll help you and Harry with your homework later on, OK?"
Her father had an apron（围裙） on over his clothes, and he looked kind of funny. He was doing the dishes and he always splashed（溅出） water all over when he did that. After helping her father with the dishes, Tammy helped set the table.
After supper, her father helped her and Harry with their homework, and then they played a board game so that their mother could lie down for a while.
The next morning, Tammy got up early on her own because she wanted to help her mother with breakfast. She made orange juice and even put bread in the toaster and got out the butter so that her mother could sleep for a few more minutes.
When her mother got up half an hour later, she was very surprised and moved to see the breakfast on the dining table. She gave Tammy a big hug.
"Thank you, Tammy. You really are mother's little helper now, aren't you?"
【小题1】Why did Tammy's sister move out of their home?