设D为AB的中点,则MA+MB=2MD,又M为△ABC的重心,
则MC=-2MD,所以MA+MB+MC=0.
故答案为0.
人体皮肤的糖原含量最高的时期是()
A.胎儿期
B.少年期
C.青年期
D.老年期
We must stress that these payment terms ( )very important to us.
A.be
B.being
C.been
D.are