Which of the following curves represents a first-order reaction?

For a first order reaction at $27^{\circ} C$,the ratio of time required for $75 \%$ completion to $25 \%$ completion of reaction is

$A$ reaction that is of the first order with respect to reactant $A$ has a rate constant $6 \ min^{-1}$. If we start with $[A] = 0.5 \ mol \ L^{-1}$,when would $[A]$ reach the value $0.05 \ mol \ L^{-1}$? (in $min$)

The rate of a first order reaction is $1.5 \times 10^{-2} \ mol \ L^{-1} \ \min^{-1}$ at $0.5 \ M$ concentration of the reactant. The half life of the reaction is ....... $\min$

The following results are obtained in one pseudo first order reaction:

Time $(s)$	$0$	$30$	$60$	$90$
Concentration $(mol \ L^{-1})$	$0.551$	$0.312$	$0.173$	$0.085$

$(a)$ Calculate the average rate of reaction between $30$ and $60$ seconds.
$(b)$ Calculate the rate constant $(k)$ of this first order reaction.

In a first order reaction,if the concentration of reactant drops from $0.8 \ mol \ L^{-1}$ to $0.4 \ mol \ L^{-1}$ in $15$ minutes,what is the time required to drop the concentration from $0.1 \ mol \ L^{-1}$ to $0.025 \ mol \ L^{-1}$?