When documenting two authors in an in$-$text citation, which is correct?

Question $7$ Select one:

a$.$

Lakoff and Johnson suggest that metaphors $$actually structure our perceptions and understanding$($Lakoff et al$.57).$

b$.$

Lakoff et al$.$ suggest that metaphors $$actually structure our perceptions and understanding$(57).$

c$.$

Lakoff and Johnson suggest that metaphors $$actually structure our perceptions and understanding$($Lakoff and Johnson $57).$

d$.$

Lakoff and Johnson suggest that metaphors $$actually structure our perceptions and understanding$(57).$