By 4000 b. c.e., how far north of the fertile crescent had horticulture spread?

Horticulture is a practice of growing plants such as fruits, vegetables, flowers among other cultivar. Also includes conservation of plants, landscape restoration, management of soil, landscape and signing of garden, construction, and maintenance, and arboriculture. Fertile crescent was a crescent shaped region where agriculture and early human civilization took place. By 4000 B.C.E horticulture had spread up to Britain which is north of fertile crescent.

It is c because it shows how the author is stating their own oppinion about the protagonist