在一个用数组实现的队列类中，假定数组长度为MS，队首元素位置为first，队列长度为length，则队首的后一个位置为(first+length)%MS。（）

A.first+1

B.(first+1)%MS

C.(first-1)%MS

D.(first+length)%MS

A.length+1

B.first+length

C.(first+length-1)%MS

D.(first+length)%MS

A.length+1

B.first+length

C.(first+length-1)%MS

D.(first+length)%MS

A．length+1

B．first+length

C．(first+length-1)%MS

D．(first+length)%MS

A．5

B．6

C．16

D．17

A.rear-front

B.(rear-front)%N

C.(rear-front+N)%N

D.(rear-front+1)%N

A.(rear-front+1)%N

B.(rear-front+N)%N

C.rear-front

D.(rear-front)%N

A.rear-front

B.(rear-front)%N

C.(rear-front+N)%N

D.(rear-front+1)%N

A.r-f

B.(m+r-f)mod m

C.(m-r+f)mod m

D.(m-r-f)mod m

A.rear-front

B.(rear-front)%N

C.(rear-front+N)%N

D.(rear-front+1)%N