Answer:
a. For the most part, early hunter-gatherers were nomadic.
c. Early humans lived in caves, rock shelters in cliffs, and in tents.
d. An achievement of early humans was the mastery of fire.
Step-by-step explanation:
Early humans had not yet mastered agriculture and so could not establish permanent settlements because they would run out of food if they stayed in one place. They therefore travelled from place to place hunting and gathering the food they needed to survive.
As the early humans were not advanced and had to move around quite often, they stayed in caves, rock shelters in cliffs and tents that they would set up in the areas they would move to.
One of the earliest achievements of early humans was the mastery of fire. With fire they were able to keep warm, cook food and most importantly, chase predators away and therefore protect themselves and establish dominance over many wild animals.