Dear Student
a) Companies use various tools at the same time because of the nature of the product and market, promotion budget and objectives of the promotion being different at different times.
b) Most commonly used non- personal tools of communication is advertising. Advertising is used to promote an idea for selling goods and services and we can communicate to various people at the same time without making any personal contact with them.
c) (i) Public relation
(ii) Advertising
(iii) Personal selling or door to door selling
(iv) Sales promotion
Regards