Which sentence has an error in subject-verb agreement?
a) sarah conner, after playing with the neighborhood girls, fell asleep in the backyard hammock.
b) the teacher opened her door to find a police officer and drug dog outside waiting to come in.
c) some employers--in fact, those who often have families of their own--give out yearly christmas bonuses.
d) joseph schultz in the next apartment, as well as the entire partridge family, have lived in our neighborhood since 1990.