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Let $\mathfrak{g}$ be positively graded Lie algebra over $\mathbb{Q}$, concentrated in even degrees.
Question: If $\mathfrak{g}$ is not free, domust there exist linearly independent elements $a,b\in\mathfrak{g}$ such that $[a,b]=0$?
Question: If $\mathfrak{g}$ is not free, do there exist linearly independent elements $a,b\in\mathfrak{g}$ such that $[a,b]=0$?
Question: If $\mathfrak{g}$ is not free, must there exist linearly independent elements $a,b\in\mathfrak{g}$ such that $[a,b]=0$?