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【单选题】
Solar Storm At the end of October 2003, a sudden solar storm hit the earth. A solar storm refers to the large amounts of charged particles released into space_________ (51) the solar energy increases. The release of the energy_________ (52) place along with the activity of the sunspots with a cycle of 11 years. This time, the_________ (53) of the storm exceeded expectations. This_________ (54) of intense solar storm was caused by the eruption of a solar flare (闪光) and the ejection (喷发)of the solar corona (日冠) on October 28, 2003. Large amounts of charged particles moved 150,000,000 kilometers through space toward the_________ (55) in 19 hours. They could affect aircraft roaming (漫游)in space. The high-energy particles will_________ (56) some of the parts of an aircraft. They may also cause it to fail. High-energy particles can threaten the safety of an aircraft at a high orbit. If an aircraft orbits at a lower orbit, it is_________ (57) because it is under the protection of the earth's magnetic field. A solar storm not only affects aircraft but also is a_________ (58) to the environment and humans. The aerosphere and magnetic field of the earth can_________ (59) humans from ultraviolet radiation and X-rays. While most of the X-rays are absorbed after they enter the aerosphere (大气层), still a few can_________ (60) the ground. The geomagnetic storm caused by this round of solar storm reaches its highest level on the two_________ (61) of the earth, which affects electricity supply of North America.Overexposure to_________ (62) threatens the health of passengers on planes flying over the PolarRegions. If we fly in the sky during such a solar storm, it_________ (63)we receive ten times the X-ray radiation. It's really damaging. Scientists say a solar eruption is like the sun sneezing, which will make the earth_________ (64)a cold.Though this natural force is irresistible, scientists can still_________ (65)its movement accur'ately by monitoring. Facing successive solar storms,humans can't drop their guard. 第 52 题
A.
since
B.
when
C.
until
D.
though
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【单选题】患儿,男,10个月。冬季出生,近1个月来睡眠不安、夜惊、多汗、枕秃,无明显骨骼改变。查血钙正常,血磷稍低,碱性磷酸酶增高,诊断为维生素D缺乏性佝偻病。请判断病期及相应维生素D的用量。
A.
初期,用治疗量
B.
激期,用治疗量
C.
恢复期,用预防量
D.
后遗症期,不用治疗
E.
初期,用预防量
【多选题】设有学生关系:S(SNO, SNAME, SEX, AGE, DEPT)。在这个关系中,SNO表示学号,SNAME表示姓名,SEX表示性别,AGE表示年龄,DEPT表示系部。查询学生姓名和所在系的投影操作的关系运算式是( )。
A.
П2, 5(S)
B.
σ2, 5(S)
C.
ПSNAME, DEPT(S)
D.
σSNAME, DEPT(S)
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A.
S∪R
B.
S-R
C.
S∩R
D.
S×R
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A.
dissuaded
B.
distracted
C.
discerned
D.
discounted
【单选题】设有如下图所示的两个关系S(sno,sname,sex)和SC(mo,eno,grade)。其中关系S的主码是sno,关系SC的主码是(sno,cno)。且关系SC的属性“sno”是它的外码。要求grade的取值只能是0~100之间的整数。 (23)关系数据库必须满足以下3类完整性规则: Ⅰ.实体完整性规则 Ⅱ.参照完整性规则 Ⅲ.用户定义的完整性规则 上述两个关系违背了哪个(些)完整性规则?
A.
仅Ⅰ
B.
仅Ⅱ和Ⅲ
C.
仅Ⅰ和Ⅱ
D.
Ⅰ、Ⅱ和Ⅲ
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A.
仅Ⅰ
B.
仅Ⅱ和Ⅲ
C.
仅Ⅰ和Ⅱ
D.
Ⅰ、Ⅱ和Ⅲ
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A.
仅Ⅰ
B.
仅Ⅱ和Ⅲ
C.
仅Ⅰ和Ⅱ
D.
Ⅰ、Ⅱ和Ⅲ
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A.
初期
B.
激期
C.
活动期
D.
恢复期
E.
后遗症期
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A.
仅Ⅰ
B.
仅Ⅱ和Ⅲ
C.
仅Ⅰ和Ⅱ
D.
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