下列4种形式的循环设计中，循环次数最少的是

A．a=5:b=8
Do
a=a+1
Loop Wbile a＜b
B．a=5:b=8
Do
a=a+1
Loop Until a＜b
C．a=5:b=8
Do Until a＜b
b=b+1
Loop
D．a=5:b=8
Do Until a＞b
a=a+1
Loop