搜题请搜索小程序“爱下问搜题”
问题 选择题

下列有关化学基本概念正确的是       

A．氧化还原的本质是存在电子的转移（得失或偏移）

B．有单质参加的化学反应一定是氧化还原反应

C．依据化合物在水溶液中的导电能力强弱，将化合物分为强电解质和弱电解质

D．溶液与胶体的本质区别是否能产生丁达尔现象

答案

答案：A

题目分析：A项氧化还原的本质是电子的转移，正确；B项有单质参加的化学反应不一定是氧化还原反应，如如3O2=2O3就不是氧化还原反应；C项依据化合物在水溶液中的电离程度，将化合物分为强电解质和弱电解质；D项溶液与胶体的本质区别是粒子直径的大小。

点评：直接考查概念的定义，属于简单题。

单项选择题

腰膝酸软而痛，眩晕耳鸣，齿松发脱，五心烦热。潮热盗汗，证属（）

A．肾阳虚证

B．肾阴虚证

C．肾虚水泛证

D．肾精不足证

E．肾气不固证
查看答案
单项选择题

Most plants can make their own food from sunlight, (1) some have discovered that stealing is an easier way to live. Thousands of plant species get by (2) photosynthesizing, and over 400 of these species seem to live by pilfering sugars from an underground (3) of fungi(真菌). But in (4) a handful of these plants has this modus operandi been traced to a relatively obscure fungus. To find out how (5) are (6) , mycologist Martin Bidartondo of the University of California at Berkeley and his team looked in their roots. What they found were (7) of a common type of fungus, so (8) that it is found in nearly 70 percent of all plants. The presence of this common fungus in these plants not only (9) at how they survive, says Bidartondo, but also suggests that many ordinary plants might prosper from a little looting, too.

Plants have (10) relations to get what they need to survive. Normal, (11) plants can make their own carbohydrates through photosynthesis, but they still need minerals. Most plants have (12) a symbiotic relationship with a (13) network of what are called my corrhizal fungi, which lies beneath the forest (14) . The fungi help green plants absorb minerals through their roots, and (15) , the plants normally (16) the fungi with sugars, or carbon with a number of plants sharing the same fungal web, it was perhaps (17) that a few cheaters—dubbed epiparasites—would evolve to beat the system. (18) , these plants reversed the flow of carbon, (19) it into their roots from the fungi (20) releasing it as "payment.\

11（）

A.green

B.land

C.wild

D.grown
查看答案