What does practical impediment mean?

What does brutus say that anticipates the question of why the crowd should listen to mark antony? o a. not that i lov'd caesar less, but that i lov'd rome more. o b. and, for my sake, stay here with antony. do grace to caesar's corpse, and grace his speech. o c. i thrice presented him a kingly crown, / which he did thrice refuse. was this ambition? od. i come to bury caesar, not to praise him.