题目

Easy Ways to Improve Your Writing Skills     For better or for worse, school is filled with writing homework. Good writing is important for getting a good grade.  36  Luckily, anyone can improve his or her writing with the right guidance and a little practice. Here are four easy tips to help you improve your writing skills: 1. Organize your thoughts first. Good writers outline their thoughts before starting putting their pens to paper or hands to a keyboard. Firstly, write out each main topic. Next, list subtopics(小标题) beneath much main topic. Lastly, put the topics and subt如图,二次函数y=ax2+bx+c的图象如图,则下列说法:①ac＜0；②2a+b＜0；③当x=1时,a+b+c＞0；④当x=﹣1时,a﹣b+c＞0；⑤关于x的一元二次方程ax2+bx+c=0有两个不相等实数根.你认为其中正确的有（ ） A. 1个 B. 2个 C. 3个 D. 4个