Which accurately describes a chart developed 20 years aftera historical event?

Assuming that this is referring to the same list of options that was posted before with this question, the correct response would be "secondary source," since this would be analyzing something in the past.

in contrast, the biological controls are self-sustaining, inexpensive and very effective once established. biological control could be used on thousands of golf course acres, improving their biodiversity and quality as wildlife habitat. in the process, the golf industry will be shown to be leaders in an environmental stewardship program of benefit not only to the lands they manage but also to the watersheds in which they exist.

the answer is c my brotha. c.   formed an alliance with the soviet union.