It is important to carefully look at all the information's that are given in the question. based on those information's the answer to the question has to be deduced. One important aspect for doing this problem is converting 1 minute into 60 seconds and then start solving.
In 15 seconds a the number of desk chairs a furniture factory can box = 1
In 60 seconds a the number of
desk chairs a furniture factory can box = (1/15) * 60
= 4 chairs
So the correct option is option "C" among all the options given in the question. As can be seen from the deduction above, 4 desk chairs per minute can be boxed by the furniture company.