8, 10, 14, 18, (...), 34, 50, 66

Answer: Option C

Explanation:

Please note that above sequence is containing 3 series
Series 1 : 8, 7, 6, (..)
Series 2 : 9, 10, 11, 12
Series 3 : 8, 9, 10

In series 1 pattern is -1. So missing term will be 6-1 = 5

Answer: Option A

Explanation:

We can judge that it is A.P.
With 6 as difference
nth term in A.P. = a+(n-1)d
a= 3, n = 21, d = 6
So, 21st term will be = 3+(20)6 = 123

Answer: Option D

Explanation:

Numerators of the fractions in the given sequence are getting increased by 2, i.e. 1+2,3+2,5+2, so next will be 7+2 = 9

Denominators of the fractions in the series is getting doubled, 2*2 = 4, 4*2 = 8, 8*2 = 16, no next will be 16*2 = 32

So resulting fraction will be
\begin{aligned}
\frac{9}{32}
\end{aligned}

Answer: Option B

Explanation:

Above series contains prime number series. So after 11, 13 is next prime number.

Answer: Option D

Explanation:

Pattern is, -1, -2, ..,.. , -5

So -3 and -4 will fill the blanks to make it a pattern.

Next number will be 17-3 = 14