$\underline{\textbf{Answer:}\Rightarrow}\;2)\;\text{only}\;b$
$\underline{\textbf{Explanation:}\Rightarrow}$
$\textbf{(i)False}$
The running time depends on the number of subproblems multiplied the time taken by each subproblem.
It will be true only in the case when the time taken by each subproblem $\mathbf{= O(1)}$.
$\textbf{(ii)True}$
$\because$ Cyclic dependency has mutually recursive modules. So, we cannot get a correct solution in DP.
$\mathbf{(iii) False}$
The reverse of the given statement is true, $\mathbf{i.e.}$ using Recursion and memoization it is faster.
$\mathbf{(iv) False}$
X must be $\textbf{NP-Complete}$ and not NP-hard.