t℃时，将一定量A（不含结晶水）的不饱和溶液均分为三份，分别加热蒸发，然后冷却至t℃，已知三份溶液分别蒸发水的质量为10g、20g、30g，析出A晶体的质量依次为a g、b g、c g，则a、b、c三者的关系为（　　）

A．c=a+b

B．c=2b-a

C．c=2b+a

D．c=2a-b

A good translator is by definition bilingual. The opposite is not ______(1) true, however. A born and bred bilingual will still need two__________(2) to become a translator: first, the skills and experience necessary for__________(3); second, knowledge of the field in which he or she will__________(4). The skills and experience for translation include the ability to write ______(5) in the target language, the ability to read and understand the_________(6) language material thoroughly, and the ability to work with the latest__________(7) and communication hardware and software.Does a born and bred bilingual__________(8) a better translator than someone who learned language B later in__________(9) There is no definite answer, but the following issues are important.__________(10), a born and bred bilingual often suffers from not truly knowing __________(11) language well enough to translate, with some even suffering from what __________(12) known as a lingualism, a state in which a person lacks_________(13) full, fluent command of any language. Second, born and bred bilinguals__________(14) don’’t know the culture of the target language well enough to_________(15) top-quality translations, or cannot recognize what aspects of the source language__________(16) its culture need to be treated with particular care, as they_________(17) in a sense too close to the language. And last, they often_________(18) the analytical linguistic skills to work through a sticky text.On_________(19) other hand, the acquired bilingual may not have the same in-depth _________(20) of colloquialisms, slang, and dialect that the born bilingual has. Also, the acquired bilingual will not be able to translate as readily in both directions (from B to language A and A to language B). Finally, born bilinguals often have a greater appreciation of the subtleties and nuances of both their languages than someone who learns their B language later in life can ever hope to have.