Final answer:
The most reasonable conclusion from the experiment is that vitamins seem to cause an increase in ink production in squids.
Step-by-step explanation:
Based on the results of the experiment where 30 squid were given vitamins and 30 were not, and the group given vitamins produced more ink on average, a reasonable conclusion would be that vitamins seem to cause an increase in ink production. Therefore, the correct answer is C. Vitamins seem to cause an increase in ink production. Answer A is incorrect because there is a difference in ink production between the two groups. Answer B jumps to a recommendation without further support or investigation. Lastly, Answer D makes a health claim that is not supported by the ink production data alone.