某二分查找程序,其VB代码如下:m = Int(Rnd*20) + 1s = 1∶t = 10∶str1=""Do While s < t If a(s) + a(t) = m Thenleft = a(s)right = a(t)s = s + 1t = t - 1 ElseIf a(s) + a(t) < m Thens = s + 1∶str1 = str1 + "R" Elset = t - 1∶str1 = str1 + " L " End IfLoop数组元素a(1)到a(10)的值依次为“1,4,4,5,5,6,7,8,8,9”,则str1的值不可能是()