只有在顶板稳定性好的情况下才可以使用锚杆支护。

患者男，缺失，缺失，拟行可摘局部义齿修复，设计RPI卡环，采用三臂卡环，舌杆大连接体连接

下列哪项不属于杆状卡环的变体（）

A.U形

B.W形

C.T形

D.I形

E.L形

腹股沟管的内环是指

A．腹膜的卵圆形裂隙

B．腹横筋膜的卵圆形裂隙

C．联合肌腱下方的薄弱部分

D．腹外斜肌腱膜的三角形裂隙

E．腹内斜肌的卵圆形裂隙

阅读理解。

     All too often, a choice that seems sustainable (可持续的) turns out on closer examination to be problematic.

Probably the best example is the rush to produce ethanol (乙醇) for fuel from corn. Corn is a renewable

resource-you can harvest it and grow more, almost limitlessly. So replacing gas with corn ethanol seems like

a great idea.

     One might get a bit more energy out of the ethanol than that used to make it, which could still make ethanol

more sustainable than gas generally, but that's not the end of the problem. Using corn to make ethanol means

less corn is left to feed animals and people, which drives up the cost of food. That result leads to turning the

fallow land -including, in some cases, rain forest in places such as Brazil-into farmland, which in turn gives

off lots of carbon dioxide (CO) into the air. Finally, over many years, the energy benefit from burning ethanol

would make up for the forest loss. But by then, climate change would have progressed so far that it might not

help.

     You cannot really declare any practice "sustainable" until you have done a complete life-cycle analysis of its

environmental (环境的) costs. Even then, technology and public keep developing, and that development can

lead to unforeseen and undesired results. The admirable goal of living sustainably requires plenty of thought on

an ongoing basis.

1. What might directly cause the loss of the forest according to the text?

A. The growing demand for energy to make ethanol

B. The increasing carbon dioxide in the air

C. The greater need for farmland

D. The big change in weather.

2. The underlined word "it" in the second paragraph refers to "_____."

A. the energy benefit

B. the forest loss

C. climate change

D. burning ethanol

3. The author thinks that replacing gas with corn ethanol is _____.

A. impractical

B. acceptable

C. admirable

D. useless

4. What does the author mainly discuss in the text?

A. Technology

B. Sustainability

C. Ethanol energy

D. Environmental protection

患者，男性，12岁，恒牙，深覆，深覆盖，上前牙唇倾，存在散在间隙约4mm，下牙列未见拥挤，双侧第一恒磨牙、尖牙呈远中关系，上颌骨发育正常，下颌后缩，ANB角为5°，诊断为安氏Ⅱ类错。最佳矫治方案为（）

A.拔双侧上下颌第一前磨牙后固定矫治器矫治

B.拔双侧上颌第一前磨牙，下颌第二前磨牙，后固定矫治器矫治

C.拔双侧上颌第一前磨牙，固定矫治器矫治

D.先不拔牙，功能矫治器调整下颌位置，固定矫治器精细调整

E.以上都是

金本位制又可分为金币本位、金块本位和金汇兑本位三种不同的形态，其中以金块本位为最典型的金本位制。