IMO C
Preliminary studies at Harvard and Ohio State, among other institutions, suggests that engaging students in class through a device as familiar to them as a cell phone increase its understanding of material that may otherwise be conveyed in traditional lectures.
A.
suggests that engaging students in class through a device as familiar to them as a cell phone increase its understanding of material that may otherwise be conveyed in --> Subject -Verb Agreement, studies need singular verb
B. suggest that to engage students in class
through familiar devices to them as a cell phone increases their understanding of material that may otherwise have to be conveyed in -> misplaced adjective
C. suggest that engaging students in class through a device as familiar to them as a cell phone increases their understanding of material that may otherwise be conveyed in --> Correct
D.
suggests that engaging students in class through a device so familiar to them as a cell phone will increase its understanding of material that may otherwise be conveyed in --> Subject -Verb Agreement
E. suggest that
while engaging students in class through a device as familiar to them as a cell phone increases the understanding of material that may otherwise be conveyed from --> while makes no sense here as it has not been used to compare or contrast correctly.