This is speculation, so please get a second opinion.
I think it's c, because the adults, in this passage, are teaching children how to behave, and therefore a and b are ruled out. d could have possibly been one, but I think that it would not be, because the adults are not explicitly setting clear examples for their children.
Again, you should get a second answer before you answer this.
They can help strengthen a point as long as the question is then enforced. They help to convince the listener since usually even thought it's not said we usually think yes in our head after hearing a rhetorical question.
D would turn out to be your answer
punta ka Google then search mo 'yang tanong mo
di'ba Sabi ni'la Alam ni google lahat ka'ya Alam ni google 'yan
