题目

— Let's meet at two o'clock this afternoon.— OK. See you.— A . Goodbye. B . I see. C . That's right. D . You're welcome. 答案：A如图，数轴上M、N、P三点对应的数都是整数,且点M为线段NP的中点．若点M对应的整数是a,点N对应的整数是b，且．则数轴上的原点是点   ▲   ．