1. The problem statement, all variables and given/known data It is sure that there is loss of species, is it possible for the vice-versa condition? a) yes, it is a must b) yes c) possible d) doubtful e) none of these 2. The attempt at a solution I thought the answer was option (a) so as to maintain the balance in nature. But my teacher told the answer was option (d). He explained by giving an exampe of an imaginary family. He asked us to consider a family: parents and 2 children. One day, the parents will die and the 2 children will eventually have children continuing the family tree. But if the 2 children happened to be sterile, or if they met with an accident resulting in death, the family will come to an end. So he said there is no guarantee that a new species have to be formed. Thus, the answer is option (d): doubtful. But can't the answer be (c): possible. Aren't we looking at negative side when we say "doubtful" and the positive side when we say "possible". Is there any further explanation that supports my teacher's answer?