The term "content adjacency" refers to:

a$.$

advertisements that are targeted based on a user's query

b$.$

problems associated with advertisements that run before a user arrives at the home page of a website

c$.$

placing advertisements to reach consumers based on various traits such as demographics and purchase history

d$.$

a concern that an advertisement will run near offensive material, embarrassing an advertiser and$/$or degrading their products or brands

e$.$

a technique used by online publishers to increase the effectiveness of their campaigns