Select the option that is related to the fourth number in the same way a the first number is related to the second number and the fifth number is related to the sixth number.

123 : 492 :: ? : 312 :: 32 : 128 

78

Pattern followed is :

2nd number = 1st number × 4

We have ,

123 : 492

2nd number = 123 × 4

= 492

&   32 : 128
2nd number = 32 × 4

= 128 

Similarly ,

? : 312

2nd number = X × 4

312 = X × 4

X = 78

78 , is correct answer .