I have four questions.

S1. Choose some letters

1.A
2.B
3.C
4.D
5.E
6.F
7.G
8.H
9.I

S2. Choose some letters
1.A
4.D
5.E
6.F
9.I

S3. Choose some letters


1.A
2.B
3.C
4.D
7.G
9.I


S4.Choose your favorite letter



I want S4 to show all the answers to S1.S2.S3, Can't repeat,

S4 I use Array filter: S1.S2.S3,

S1 Choose 1,2

S2 Choose 1,4

S3 Choose 1,3

S4 shows answer 1.

I want to show 1 (A), 2 (, 3 (C), 4 (D).

What should I do?