单项选择题
A．students have to read the whole book B．students have not enough time to finish the book C．students often fail to get the main idea of the book D．students usually get more useless information
A．they cover major points of the book in detail B．they may help reader to better understand the book C．they can take readers a lot of time to read every part of the book D．they may help the readers find the important parts of the book
A．Positive. B．Critical. C．Neutral. D．Indifferent.