The materials and information we post online:

a. give others a snapshot of ourselves.-
b. will someday be used against us.
c. provide a full picture of our lives.
d. do not show much about who we are.

I would personally choose A as my answer

As when one glances at a social media page, they are going to find bits of information that make up who you are as a person and your interests.

I would argue against b, as this is not necessarily true even though there is a remote possibility. C seems incorrect to me as it seems very hard to truly encompass someone's entire life and all that has occurred online. Finally, d does is false for obvious reasons. If you decide to fire back at a bully someone over the internet that could easily be interpreted as insecurity by an individual. Same goes for the other side of the spectrum, if you use you platform to share joy and kindness, you are most likely a caring person in some manner.  

answer; social structure;