In this task, you need to answer the given multiple-choice question on the general math. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Problem: a is two years older than b who is twice as old as c . if the total of the ages of a , b and c be 12 , the how old is b ? 
Options: a ) 10 years , b ) 4 years , c ) 6 years , d ) 15 years , e ) 16 years
b

Problem: find value for x from below equation ? x + 1 = 4 
Options: a ) - 5 , b ) - 4 , c ) 4 , d ) 3 , e ) 2
d

Problem: if n = ( 33 ) ^ 43 + ( 53 ) ^ 33 what is the units digit of n ? 
Options: a ) 0 , b ) 2 , c ) 4 , d ) 6 , e ) 8

c