Answer:
A. 4
Step-by-step explanation:
Of 18 free samples 10 are recommended by a magazine. Six of those are produced by large companies. You want to know the number recommended by a magazine that have not been produced by large companies.
Of the 10 samples recommended by a magazine, 6 are produced by large companies. The remaining 4 are not.
4 of the samples are not produced by large companies, but have been recommended, choice A.