Verbal Reasoning - Mental Ability Questions

CAT : MOUSE as SNAKE : 

Select the missing numbers from the given alternatives.

Select the missing number from the given responses?

In the following question, which one set of letters when sequentially placed at the gaps in the given letter series shall complete it? 

p_r_s_q_p_rs

Select the missing numbers from the given alternatives

In the following question, select the related letter from the given alternatives.
DE : O : : AF : ?

In the following question, select the related letter pair from the given alternatives. MOK : KLG : : ? : ?

A series is given with one term missing. Choose the correct alternative from the given ones that will complete the series.

7, 49, 343, ?