Awriter should avoid relying heavily on one source in an informational text because [blank] . a) it increases the potential for plagiarism b) the writer should synthesize information from various sources in order to convey original ideas

B) The writer should synthesize information from various sources in order to convey original ideas

Explanation:

If you are relying on one source to writte your text, you might as well just present that document, you have to come up with your own ideas and explain and elaborate them, by revising several sources you´ll have more information and this would allow you to be more original and have new theories and thesis.

the correct answer would be:  

a. adverb phrase

i believe the answer is a