Which property is demonstrated? 8*1*6=6*1*8
a. associative property of multiplication
b. communicative property of multiplication

This is an associative property of multiplication.
because Associative property of multiplications show that you can multiply numbers regardless of how it is grouped. In the end, the answer will still be the same
Given equation = 8 x 1 x 6 = 6 x 1 x 8
=> 8 x 1 x 6 = 6 x 1 x 8
=> (8 x  1) x 6 = (6 x 1 ) x 8
=> 8 x 6 = 6 x 8
=>  48 = 48