Aptitude

✅ The correct answer is option C.
There are two series, beginning respectively with 3 and 7. In one 3 is added and in another 2 is subtracted.
The next number is 1 – 2 = -1.

✅ The correct answer is option D.
Each of the numbers is a prime number except 12.

✅ The correct answer is option B.
Each of the numbers except 72 is a perfect square.

✅ The correct answer is option D.
(1*1)+1 , (2*2)+1 , (3*3)+1 , (4*4)+1 , (5*5)+1 , (6*6)+1 , (7*7)+1 , (8*8)+1
But, 64 is out of pattern.

✅ The correct answer is option A.
In each number except 751, the difference of third and first digit is the middle one.

✅ The correct answer is option B.
Go on adding 7, 9, 11, 13, 15, 17 respectively to obtain the next number.
So, 33 is wrong. It must be 35

✅ The correct answer is option C.
The pattern is 12, 22, 32, 42, 52, 62, 72. But, instead of 52, it is 20 which to be turned out.

✅ The correct answer is option A.
The numbers are squares of odd natural numbers, starting from 5 up to 15.
So, 36 is wrong.

✅ The correct answer is option A.
Alternatively 23 is added and 17 is subtracted from the terms. So, 634 is wrong.

✅ The correct answer is option A.
Each number is twice the preceding one with 1 added or subtracted alternatively.
So, the next number is (2 x 261 + 1) = 523.