问题
选择题
甲站在岸上，乙潜入清澈的水中站立，二人互相对看.甲、乙看到对方的头部位置
A．都比实际位置高
B．都比实际位置低
C．甲看乙低，乙看甲高（与实际位置比较）
D．甲看乙高，乙看甲低（与实际位置比较）
答案
答案：A
如图所示，A为水中的人，D为岸上的人，D看到的A发出的光线为CD，所以A的像为B，变高.根据光的可逆性原理,A看到的D的像为E，也变高了.
搜题请搜索小程序“爱下问搜题”
甲站在岸上，乙潜入清澈的水中站立，二人互相对看.甲、乙看到对方的头部位置
A．都比实际位置高
B．都比实际位置低
C．甲看乙低，乙看甲高（与实际位置比较）
D．甲看乙高，乙看甲低（与实际位置比较）
答案：A
如图所示，A为水中的人，D为岸上的人，D看到的A发出的光线为CD，所以A的像为B，变高.根据光的可逆性原理,A看到的D的像为E，也变高了.
| About fifty years ago, plant physiologists set out to grow roots by themselves in solutions in laboratory flasks. The scientists found that the nutrition of isolated roots was quite simple. They required sugar and the usual minerals and vitamins. However, they did not require organic nitrogen compounds. These roots got along fine on mineral inorganic nitrogen. Roots are capable of making their own proteins and other organic compounds. These activities by roots require energy, of course. The process of respiration uses sugar to make the high energy compound ATP, which drives the biochemical reactions. Respiration also requires oxygen. Highly active roots require a good deal of oxygen. The study of isolated roots has provided an understanding of the relationship between shoots and roots in intact plants. The leaves of the shoots provide the roots with sugar and vitamins, and the roots provide the shoots with water and minerals. In addition, roots can provide the shoots with organic nitrogen compounds. This comes in handy for the growth of buds in the early spring when leaves are not yet functioning. Once leaves begin photosynthesizing, they produce protein, but only mature leaves can "export" protein to the rest of the plant in the form of amino acids. |
The underlined word "intact" in Paragraph 2 is closest in meaning to ______.
A．mature
B．wild
C．whole
D．tiny