Bunuel
Even though the law mandates that all passengers in a vehicle wear a seat belt, still approximately 20% of the population refrains from doing so.
Elimination round 1:
A.
Even though the law mandates that all passengers in a vehicle wear a seat belt,
still approximately - redundancy
D. The law mandates that all passengers in a vehicle
will wear a seat belt, yet around - tense
E. Even though the law mandates that every passenger in a vehicle
is wearing a seat belt, approximately - tense
Elimination round 2: Let's see the differences.
B.
Even though the law mandates that
every passenger in a vehicle
wears a seat belt, approximately
C. The law mandates that
all passengers in a vehicle
wear a seat belt,
still approximately
With "Even though", one might think that the contrast and meaning are much more clear in option B, the subjunctive (mandate + wear) is the deciding factor here.