People usually access social networking sites to be informed and entertained, as well as to connect to others and:
o a. outline their thoughts.
o b. earn better grades.
o c contribute or create something.
o d. buy digital media.

A. outline their thoughts.  

Explanation:

Social networks are used to inform, entertain, connect with others, and outline your thoughts. This is because the interaction that social networks provide, lets the people form their opinions, delineating their thoughts about something, through some information they see, or the comment that a friend made, or the photo that was posted.

explanation:

allergens: overstimulate the nerve system

neurotics: attack nerve cells

mutagens: damage or otherwise alter dna sequence

generators: cause defects during growth and development  

carcinogens: cause unchecked cell growth

i hope you get the idea according to me these are the effects that happened.