ANSWER :
B : Partnership
EXPLANATION :
A group of people (less than 10 in banking, less than 20 in other) carrying on a business together, deciding to share profits or losses in a proportion (based on a contract) , mutual agency (one partners' act effecting other) , unlimited liability of partners towards outsiders (except for special limited liability partnership) .
All these characteristics are satisfied by venture of Franklin , John , Harry & Henry.
Sole Proprietorship is a business owned , run & managed by a single owner. Corporate / Company is seperate legal entity from its owners (big group than partnership) ,owners don't have unlimited liability . So Franklin , John , Hary , Henry firm is not case for either one .