The goal is to derive $\varphi$ from the premises in $\Gamma$. If we can derive $\varphi$, then $\Gamma \models \varphi$. If we cannot, then it does not hold.
Let's analyze each sub-problem.
**Part a)**
$\Gamma = \{((d \lor s) \to p), (c \to \neg p), (\neg c \to
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