关于二次函数y=ax²+bx +c图像有下列命题：

（1）当c=0时，函数的图像经过原点；

（2）当c >0时，函数的图像开口向下时，方程ax²+bx+c =0必有两个不等实根；

（3）当b=0时，函数图像关于原点对称。其中正确的个数有[ ]

A.0个

B.1个

C.2个

D.3个

XP is (71) of interesting twists that encourage one to think--for example, how about "Test and then code" I’ve worked with software companies and a few IT organizations in (72) programmer performance was measured on lines of code delivered and testing was measured on defects found-- (73) side was motivated to reduce the number of defects prior to testing. XP uses two types of testing: unit and functional. (74) , the practice for unit testing involves developing the test for the feature prior to writing the code and further states that the tests should be automated. Once the code is written, it is immediately (75) to the test suite bringing instant feedback.

（71）处填（）。

A．filled

B．stuff

C．pack

D．full