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The temperature at which oxygen molecules have the same root mean square speed as helium atoms have at $\newline$$300\,\text{K}$ is :$\newline$(Atomic masses: $\newline$$\text{He}=4\,\text{u}$,$\text{O}=16\,\text{u}$ )$\newline$($1$) $\newline$$1200\,\text{K}$$\newline$($2$) $\newline$$600\,\text{K}$$\newline$($3$) $\newline$$300\,\text{K}$$\newline$($4$) $\newline$$2400\,\text{K}$