A newly discovered radioisotope has a half life of 25 days. How many days will have passed when 12.5% of the sample remains?

the population of unionid mussels in the hudson river decreased after zebra mussels were introduced. zebra mussels, a nonnative species, competed with the unionid mussels for food. the zebra mussels were able to outcompete the unionid mussels, allowing the zebra mussel population to increase dramatically over six years. the unionid mussel population decreased due to a lack of food.

hope this :

answer would be option a) they have mobile charged particles.