2・13 If the equation $(m+2) x^{2}-2(m+1) x+m=0$ has only one real root, then the equation $(m+1) x^{2}-2 m x+m-2=0$
(A) has no real roots.
(B) has two distinct real roots.
(C) has two equal real roots.
(D) the number of real roots cannot be determined.
(China "Zu Chongzhi Cup" Junior High School Mathematics Invitational Competition, 1995)