Which word in the sentence is the indirect object?

the instructor assigned each child a partner.

a.
instructor

b.
partner

c.
child

d.
each

For me the answer is letter c. child because in my own understanding indirect object is a noun phrase that refers someone or something which is affected by the action of the verb. So in the sentence "The instructor assigned each child a partner" the verb is assigned and the indirect object is child.