this is gp because
because ratio of next term to previous term is always same.
8/16= 4/8 = 1/2
so common ratio is 1/2
first term is a = 16
so nth term of a gp is given as
Tn = ar^(n-1)
T10 = 16 × (1/2)^(10-1)
= 16 × (1/2)^9 = 1/32