Initial rate data for $\mathrm{A}+\mathrm{B}\to \mathrm{products}$ (concentrations in $\mathrm{mol}{\mathrm{L}}^{-1}$, rates in $\mathrm{mol}{\mathrm{L}}^{-1}{\mathrm{s}}^{-1}$): Experiment 1: $[\mathrm{A}]=0.10$, $[\mathrm{B}]=0.10$, rate $=5.0\times 10^{-4}$. Experiment 2: $[\mathrm{A}]=0.20$, $[\mathrm{B}]=0.10$, rate $=1.0\times 10^{-3}$. Experiment 3: $[\mathrm{A}]=0.10$, $[\mathrm{B}]=0.20$, rate $=2.0\times 10^{-3}$. Experiment 4: $[\mathrm{A}]=0.20$, $[\mathrm{B}]=0.20$, rate $=4.0\times 10^{-3}$. Select the correct statement(s).

1. AThe reaction is first order in $\mathrm{A}$.
2. BThe reaction is first order in $\mathrm{B}$.
3. CThe rate constant is $0.50{\mathrm{L}}^2\mathrm{mo}{\mathrm{l}}^{-2}{\mathrm{s}}^{-1}$.
4. DThe initial rate at $[\mathrm{A}]=[\mathrm{B}]=0.30$ is $1.35\times 10^{-2}\mathrm{mol}{\mathrm{L}}^{-1}{\mathrm{s}}^{-1}$.