有三个关系R、S和T如下： 由关系R和S通过运算得到关系T，则所使用的运算为
题型：单项选择题
问题：
有三个关系R、S和T如下：
由关系R和S通过运算得到关系T，则所使用的运算为
题型：单项选择题
The Donkey Mobile Library
It is a bright morning in the Ethiopian countryside. Yohannes walks beside a pair of donkeys that are pulling a two-wheeled cart. They arrive at the agricultural town of Awassa where Yohannes opens the sides of the cart to display, not the usual vegetables or tools, but children’s books. This is the Donkey Mobile Library, the first of its kind in Ethiopia and one of only a few in the world.
Yohannes was born in Ethiopia, North Africa, but trained to be a librarian in the USA and returned to Ethiopia years ago. The cart is full of picture books donated by American libraries, teachers and school children.
Yohannes arranges small painted benches in the shade of the trees, and suddenly Ethiopian children come shouting and racing down every road and path. It’s mobile library day! They circle the bookshelves with great excitement. Until the Donkey Mobile Library began its regular two-monthly visits, many of these children had never seen a book.
“Without books, education is very dull, like food without salt. You can survive but you can’t really come alive,” says Yohannes. “The ability to read is the basis for greater productivity, better health and longer life. Even though the children lack material goods, with books they can imagine a world of possibilities.”
Yohannes first worked in the children’s section of the main library in America. Surrounded by books he had never seen before, he realized how joyful and imaginative children’s literature is. He says, “I always thought of Ethiopia. But how could I bring children’s books to my home country when it had almost no libraries to keep the books in?”
He contacted Jane Kurtz, a writer born in America but brought up in Ethiopia, and together they created the Donkey Mobile Library. The children say that the Library has given them ideas about what they might do in the future. A child called Dareje wants to be a scientist and find a cure for life-threatening diseases. An eleven year-old girl, Fikerte, wants to do research about the moon and discover new facts about outer space. Tamrat, aged 10, comes every time.
“What brings you back here time and time again?” the librarian asks him.
“The stories,” Tamrat replies instantly.
小题1:How do the children feel when they see the Donkey Mobile Library?
A．Excited.
B．Surprised.
C．Interested.
D．Curious小题2:We can conclude from the passage that .
A．Ethiopian children have no idea about their future
B．Yohannes and Kurtz share similar life experiences
C．most books in the Donkey Mobile Library were bought in America
D．donkey carts in Awassa usually carry vegetables and tools小题3:According to the passage, the Donkey Mobile Library .
A．visits the countryside every day
B．was created by Yohannes himself
C．benefits Ethiopian children a lot
D．was the first of its kind in the world小题4:Where is the passage most likely to have been taken from?
A．A book review..
B．A news report
C．A historical story.
D．An advertisement.