牛顿第一定律：一切物体在没有受到外力作用时，总保持 状态或 状态．
静止，匀速直线运动
（本小题满分14分）
已知函数f(x)=xlnx，g(x)=f(x)+f(m－x)，m为正的常数
(1)求函数g(x)的定义域；
(2)求g(x)的单调区间，并指明单调性；
(3)若a>0，b>0，证明：f(a)+(a+b)ln2≥f(a+b)－f(b)
Had they known what was coming next, they ________ second thoughts.[ ]
A. may have
B. could have
C. must have had
D. might have had
