关系运算理论中，关系R和S分别在第I(1)和第j(2)上的连接运算写成RS，其中θ是(3)。若R是r关系，则有RS=(4)。关系代数的基本操作是(5)。
A．行
B．列
C．个记录
D．张表

Young men often give flowers to young women when they are in love. This tradition may have come from Turkey. In the 1700s in Turkey, it was quite popular for people in love to send each other baskets full of strange things. The baskets were delivered secretly to the person who was receiving it. Usually, an old woman who sold flowers or fruit on the street left the basket beside the person's door. These baskets included a variety of 'gifts': flowers, stones, feathers, wax, and even charcoal. Each thing in the basket had a special meaning. By figuring out the secret message contained in each item, the person who received the basket began to understand little by little the true feelings of the person who sent it. (50) This idea of sending gifts of love with secret meanings quickly spread to Germany, France and England. However, as time passed, only sending flowers remained popular. An innocent bunch of flowers told young ladies about the feelings in the hearts of young men. Each different flower held a different meaning. For example, the flowers from an orange tree meant, 'You are beautiful and pure.' Pink carnations meant, 'My love for you is strong and great.' Yellow roses, on the other hand, meant, 'I saw you with someone else. ' Many flower dictionaries were made to help young people in love understand the meaning of the flowers they received. Not all of the dictionaries agreed, however, on the meaning of each flower, so a person had to be careful about the flowers they chose to send. By the 1880s, using flowers to send messages had fallen out of fashion, and the more direct way of sending love letters began. Today, flowers are still considered a lovely gift, but the meaning for each kind of flower has been lost.Paragraph 1 and 2 describe the tradition of______.A．sending gift basketsB．sending love lettersC．selling flowersD．sending dictionaries

A.
B.
C.
D.'
E.'
F.
Paragraph
G.
A．sending
H.sending
I.selling
J.sending

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A．情绪改变，嗜睡，呕吐 B．颅神经损伤 C．脑膜刺激征：项强(+)，克氏征(+) D．惊默，昏迷 E．右侧肢体偏瘫 以下疾病的表现为结核性脑膜炎早期

A.情绪改变，嗜睡，呕吐
B.颅神经损伤
C.脑膜刺激征：项强(+)，克氏征(+)
D.惊默，昏迷
E.右侧肢体偏瘫

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