题目内容

为了传递动力,轴上常装有齿轮、V带轮,多利用键来连接,因此在轴上加工有( )。

A. 键槽
B. 孔
C. 销孔
D. 退刀槽

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盘盖类零件有径向尺寸和轴向尺寸。径向尺寸的设计基准为( )。

A. 左端面
B. 右端面
C. 轴线
D. 较大的轮廓线

轴套类零件有径向尺寸和轴向尺寸。径向尺寸的设计基准为( )。

A. 左端面
B. 右端面
C. 轴线
D. 轴肩

盘盖类零件有径向尺寸和轴向尺寸。轴向尺寸的设计基准为( )。

A. 经过加工并与其他零件相接触的较大端面
B. 轴线
C. 键槽底面
D. 盘盖外缘

Under federal law, foods and vegetables can be 1. ______ organic if they grow without conventional pesticides or petroleum-based fertilizers (有机肥料). As a result, organic foods contain fewer 2. _______ residues. But it is unclear whether this really makes the food more healthful since pesticide levels in regular produces have not been 3. ______ to pose a healthy 4. _______ to humans.Another claim is that organic produce is more nutritious than the conventional kind. The 5. _______ for this is mixed with most studies finding no advantage for organic. Then there is a 6. _____ that organic produce is less likely to be 7. ___________ by bacteria like E. coli (大肠(杆)菌). In this case, the answer is clear — not true.What about meat and dairy products labeled organic? This means they came from animals that were not given growth hormones or anti-biotics. Though some researchers suggest that hormones in food could be 8. __________ to certain cancers and early puberty(青春期), it is a matter of scientific 9. ______. There's greater agreement that anti-biotics in the food supply may help spawn so-called “superbugs”(超级病菌) and 10. _____ us in a resistance treatment.

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