Research has shown that a child reading the sentence "Each student was instructed to return his exam to the teacher" is likely to envision __________ if the child is a boy and __________ if the child is a girl.

a. a female student; a male student
b. a male student; a male student
c. unknown; unknown (research on this topic has not been done)
d. a female student; a female student
e. a male student; a female student