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SQL2提供事务的四种隔离级别，其中最高级别是（ ）
A
SERIALIZABLE
B
REPEATABLE READ
C
READ COMMITTED
D
READ UNCOMMITTED
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试题答案：
A
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21．下列哪些因素制约外币期权交易的保险费率？
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Passage4Ancient people had litle idea of the nature of the cart's surface. But if they lived on the scashore, they knew that there was land and sca.People who lived near the sca noticed that there were two kinds of land. There were, first, litle pieces of land surrounded by sca. One Latin word for "sca" is "salum", which mcans“"salt". This is because sea water, unlike rain-water, contains sl--it is saly. So a piece of land in the sca was "in sal" in Latin, and this became isle in English.Then there was anoher kind of land that went on and on. It was "continuous" land, and so became known as contincnt in English from the Latin "continents" meaning continuous In English, we also speak of a continent as the minland ("main" comes from the Latin "megnus" me aning "great"), as opposed to isand (islc-land),To the ancient Greck there scemed to be three conincnts scparated by sca. The Mediterancan Sea, in fact, gets is name from the Latin "medius" (middle) and "terra"(land). It was a sca that lay in the middle, with three bodies of land around it. The three continents-Asia, Europe and Africa-are actually connected by land. Africa and Asia are connccted by only the small Sinai Isthmus, from the Greck "isthmus" meaning "a narrow passage", but Europe and Asia are connected by land for a thousand miles or more and it is cusomary to speak of Europe as a contincnt Many gographers speak of the landmass of Asia plus Europe as Eurasia, and Eurasia plus Afica is sometimes called the WorldIsland. The three logether are srrounded by sea, so they fom a large island, and they contain about 85 percent of the carth's population.
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9．《大学》提出教育的最高目标是
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