Most of what we know about the Olmec civilization comes from A.
their books and writings.
B.
the stories of Aztec historians.
C.
the diaries of Spanish explorers.
D.
their sculptures and artifacts.

Their sculptures and artifacts.

Explanation:

The Olmecs were extremely talented artists and sculptors: they produced many statues, masks, figurines (Yes, figurines were a thing back then), stelae (I know you're confused. A stela (the singular form of stelae) is an upright stone or column typically bearing a commemorative inscription or relief design, often serving as a gravestone.), thrones and more. However, they are best known for their colossal heads, 17 of which have been found at four different archaeological sites.

The first picture is an Olmec head, and the second is a stela.

3.a

4.d

5.b

6.b

7.c

8.a

9.d

10.a

china unilaterally claims the entire south china sea as sovereign territory, then builds artificial islands to bolster its claim. it suddenly activates an air defense identification zone over the east china sea, and threatens to down any aircraft that does not report its position. it builds roads into indian territory, then redraws the maps to show that it is actually chinese territory. the people's republic under president xi jinping is quickly becoming the bully of asia.