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问题 单项选择题 A1/A2型题

口咽肿瘤最常见的颈淋巴结转移区为（）。

A.Ⅰ～Ⅵ区

B.Ⅰ区和Ⅱ区

C.Ⅳ区和Ⅴ区

D.Ⅱ区和Ⅲ区

E.Ⅰ～Ⅴ区

答案

参考答案：D

解析：口咽淋巴引流丰富，容易出现淋巴结转移，其转移几率与原发肿瘤大小、分化程度和病期早晚相关。口咽部肿瘤在确诊时颈淋巴结转移的阳性率可达50%～70%。其中最常见的颈淋巴结转移区为Ⅱ和Ⅲ区淋巴结（即二腹肌下组和上颈深组淋巴结）。Ⅰ、Ⅳ、Ⅴ均较少出现转移，但在放疗时仍应包括在照射靶区内。

多项选择题

海的“贯通东流”水系的形成年代。如果说上游的沉积物从青藏高原、四川盆地顺延而下能到达下游，这就表明长江贯通了，这就是物源示踪。我国科学家采用这一方法研究长江中下游盆地沉积物的来源，从而判别长江上游的物质何时到达下游，间接指示了长江贯通东流的时限。他们经过10多年的研究，提出长江贯通东流的时间距今约2300多万年。这一研究成果从一个侧面显示出()。

A.时间和空间是有限的，物质运动是永恒的 

B.时间和空间是通过物质运动的变化表现出来的 

C.时间和空间是指标示物质运动的观念形式 

D.时间和空间是物质运动的存在形式
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单项选择题

The blue of the sea is caused by the scattering of sunlight by tiny particles suspended in the water. Blue light, being of short wavelength, is scattered more efficiently than light of longer wavelengths. Although waters of the open ocean are commonly some shade of blue, green water is commonly seen near coasts, especially in tropical or subtropical regions. This is caused by yellow pigments being mixed with blue water. Phytoplankton are one source of the yellow pigment. Other microscopic plants may color the water brown or brownish-red. Near the shore, silt or sediment in suspension can give water a brownish hue. Outflow of large rivers can often be observed many miles offshore by the coloration of suspended soil particles.Marine phytoplankton (Greek for "plant wanderers") are microscopic single-celled plants that include diatoms, dinoflagellates, coccolithophorids, green algae, and blue-green algae, among others. The growth of these organisms, which photosynthesize light, depends on a delicate balance of nutrient enrichment via vertical mixing, which is often limited by the availability of nitrogen and light. Diatoms are one-celled plants with patterned glass coverings. Each glass, or silicon dioxide box, is ornamented with species-specific designs, pits, and perforations making them popular with microscopists and, more recently, electron scanning microscopists.

The growth of phytoplankton is often limited by the availability of________.

A．oxygen

B．hydrogen

C．nitrogen

D．carbon dioxide
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