0 × 0 = 0
0 × 1 = 0
1 × 1 = 1
Which means multiplication is closed under {0, 1}
1 ÷ 1 = 1
0 ÷ 1 = 0
Division is not closed under {0, 1}
1 + 1 = 2
Addition is not closed under {0, 1}
0 - 1 = -1
Subtraction is not closed under {0, 1} either
So it's only A. Multiplication which is closed under {0, 1}