Final answer:
Option C. The snails in test tube A died between 7 and 14 days. From this information, we can deduce that the snails in test tube A died between 7 and 14 days, which is equivalent to 15 hours.
Step-by-step explanation:
The question asks us to determine when the snails died in test tube A. To do this, we need to refer to the provided information. In the experiment, two petri dishes were used, with dish A wrapped completely in an opaque cover to exclude all light, and dish B left uncovered. Both dishes were exposed to a cycle of 14 hours of light and 10 hours of dark. The dishes were examined after 7 days and the opaque cover was permanently removed from dish A. The dishes were then examined again at 14 days. From this information, we can deduce that the snails in test tube A died between 7 and 14 days, which is equivalent to 15 hours.
The question "When did the snails die in test tube A?" seems to be unrelated to the provided experimental information about tobacco seeds, bacteria, and bacterial endospores. Therefore, without the context or results of the experiments regarding the snails in test tube A, it is not possible to accurately determine when the snails died. An experiment involving snails would typically need specific data on the conditions of the test tube, observations at various time points, and any changes in the snails' behavior or physiology before one could determine their time of death.