【程序】 SET TALK OFF INPUT “X＝” TO X DO CASE CASE X＞10 “OK1” CASE X＞20 “OK2” OTHERWISE “OK3” ENDCASE SET TALK ON RETURN

程序运行时输入X值为15，则显示结果为 ______。

A．DO WHILE I＜M
B．FOR I=2 TO M/2
C．FOR I=M TO 1 STEP -1
D．FOR M＝I TO 0 STEP-1

A．“OK1”
B．OK1
C．“OK2”
D．“OK3”