Blue chaff disease of oats is due to deficiency

Find the missing term:

Select the missing number from the given responses. 

Select the option that is related to the third number in the same way as the second number is related to the first number.

15 : 5 :: 26 : (?)

Select the missing number from the given alternatives:

E/M ∶ 20/156: : G/O: ?

Study the given pattern carefully and select the number that can replace the question mark (?) in it.

Find the missing letter.

Find the missing number.

What number should replace the question mark?