Andre's daughter is old enough to walk to school by herself, but he is still a bit nervous about her going on her own. After speaking with some other parents, Andre found that there are multiple options for GPS trackers that he can place on his daughter's clothing, which can help ease his mind. He could also get her a cellphone, as suggested by another dad. Andre has so far used what type of source for his information search?

a$.$ Consumer$-$to$-$consumer reviews

b$.$ Nonmarketing$-$controlled information source

c$.$ Internal information

d$.$ Marketing$-$controlled information source