Select the option which is related to the fourth term in the same way as the first term is related to the second term and the fifth term is related to the sixth term.
8 ∶ 508 ∶∶ ? ∶ 2193 ∶∶ 2 ∶ 4

Let's investigate the logic between the given number pairs:
Third pair: 2:4

2
3
−4=8−4=4
First pair: 8:508

8
3
−4=512−4=508
So the rule is: Second Term=(First Term)
3
−4.

Now let's find the missing first term (x) for the second pair where the second term is 2193:

x
3
−4=2193
x
3
=2193+4
x
3
=2197
Taking the cube root of 2197:

x=
3

2197

​
=13
Thus, the missing term is 13.