1. (2020高二上·宁波期中) 有如下VB程序段

Dim a(1 to 5) as integer

Dim b(1 to 20) as integer

a(1)=10: a(2)=9: a(3)=17: a(4)=18: a(5)=13

for i=1 to 5

b(a(i))=b(a(i))+1

next i

num =0

for j=1 to 20

for k=1 to b(j)

num=num+1

a(num)=j

next k

next j

执行该程序段后，数组元素a（1）到a（5）的值依次为（    ）