The answer is A, B, and C.
D. is too broad a term that actually includes A-C. So in other words there is no company that specializes in "Technology"
There are companies that specialize in E-Commerce, Hardware, and Security.
I guess if you wanted to say Google and Apple are technology companies you could say that but even they would fit into a particular classification. Google would be a Search Engine technology, and Apple would probably still be considered a hardware company even though both companies are involved across all of the 3 subjects in the answer.
