colony and perhaps in removing dirt from the tunnels.
Jarvis’ work has suggested that differences in growth rates
may influence the length of time that an individual performs
(30) a task, regardless of its age.
Cooperative breeding has evolved many times in verte-
brates, but unlike naked mole rats, most cooperatively
breeding vertebrates (except the wild dog, Lycaon pictus)
(35) are dominated by a pair of breeders rather than by a single
breeding female. The division of labor within social groups
is less pronounced among other vertebrates than among
naked mole rats, colony size is much smaller, and mating
by subordinate females may not be totally suppressed,
(40) whereas in naked mole rat colonies subordinate females are
not sexually active, and many never breed.
1. Which of the following most accurately states the main
idea of the passage?
(A) Naked mole rat colonies are the only known
examples of cooperatively breeding vertebrate
societies.
(B) Naked mole rat colonies exhibit social organization
based on a rigid caste system.
(C) Behavior in naked mole rat colonies may well be
a close vertebrate analogue to behavior in eusocial
insect societies.
(D) The mating habits of naked mole rats differ from
those of any other vertebrate species.
(E) The basis for the division of labor among naked
mole rats is the same as that among eusocial insects.
2. The passage suggests that Jarvis’ work has called into
question which of the following explanatory variables