Answer:
a. the immediate freeing of all enslaved people.
Step-by-step explanation:
One demand of the abolition movement in the 1800s was the immediate freeing of all enslaved people (Option A).
The abolition movement was a social movement that sought to end the practice of slavery in the United States and other countries in the 19th century. The abolitionists believed that slavery was morally wrong and that enslaved people should be granted their freedom immediately.
Option B, the gradual freeing of some enslaved people, was a demand of some abolitionists as well but not of all.
Option C and D are not demands of abolition movement as they are looking for the end of the trade, not an increase or restoration of it.