In general, for a new cultural trait to be adopted by a culture, it must offer some over an existing trait.

a. benefit
b. diversity
c. diffusion
d. drawback

For people to adopt something, it should generally be good in some way: this way people will want to adopt it.

One word for "good for someone" is "beneficial: so this is the correct answer.

Other answers either mean the opposite of beneficial (d) or just refer to the process of spreading (B and C).

Ihave no idea. about. that