单选题

下列四段程序中，属于循环结构的是（ ）

Question

A. a = 10                                                                               b = 20                                                                              b = a + b                                   

B. If  score>=60  Then                                                             Msgbox("合格")                                                                    End If

C. For I = 1 to 10 step 2                                                              j = j + 1                                                                          End If

D. If  a>b  Then                                                                       a = b * b                                                                            Next  I