Locksmiths: select the best answer choice. a) install and repair locks b) are often self-employed c) learn their skills on the job d) can be classified as all of the above

I believe it is D. All of the above. 

1.) They do repair locks. 
2.) they do often offer their own services from their own company/
3.) I think they learned their skills on the job or knew someone who taught them. 

D. A locksmith can be classified as all of the above