Abortion means
a. expulsion of fetus before 28th week of gestation.
b. expulsion of fetus before 18th week of gestation.
c. expulsion of fetus before 14th week of gestation.
d expulsion of fetus before 10th week of gestation.

1. in what ways have non-native species been beneficial? 2. what are some of the hypotheses for the collapse of honeybee colonies? 3. distinguish between regional and functional extinction. 4. why is it difficult to measure background extinction rates? 5. what three factors are most important in causing extinction rates to climb?