(c) 10 cm
Explanation:
Let ABCD be rhombus with AC and BD diagonals.
Let AC and BD bisect at O.
Therefore AO = 16/2=8
BO = 12/2=6cm
In right angled triangle AOB, by Pythagoras theorem we can write as
AB2=AO2+OB2
AB2=82+62
AB2= 64 + 36
AB= √ 100
AB =10
Length of rhombus is 10 cm