3. (b) That's correct. In order to determine whether a person is engaged as an employee or independent contractor, the best approach is to examine whether the person in question can be identified as part of the defendant's enterprise or not.
Relevant factors are whether the defendant can control what the person in question does and how they do it, whether the person in question uses their own tools and materials, the method of payment and tax deductions, whose uniforms (if any) are worn, the building up of business goodwill by the person in question, and the employed person's relative freedom to work when they choose.
In the present case, B appears to be an independent contractor. He owns the crane he uses and does not seem in any way to have become part of A's business enterprise.