A large flock of endemic birds is discovered on a remote island. There appears to be two similar but different kinds of birds within the flock. Which of the following information is most important in deciding whether the two kinds of birds belong to a single species?
a) whether both kinds of males sing similar songs
b) whether both kinds of birds eat the same range of food
c) whether the matings between kinds produce viable offspring
d) whether both kinds mate with one another
e) whether both kinds share many physical characteristics

Option C

Explanation:

There are cases when two organism of different species mate to produce offspring but that offspring is unable to reproduce further.  Hence, such organisms do not belong to the same species. Thus, Option D is incorrect

However, when two organisms are able to reproduce viable offspring, they are said to be of the same species. Such organisms are also similar in looks.  

Hence, option C is correct

glacial erosion, the picking up and movement of earth beneath a glacier, is also referred to as plucking. erosion and transportation of individual pieces of bedrock, especially large "joint block occur as a result of this glacial erosion. plucking is type of erosion in which rocks become frozen into the bottom and sides of the glacier.as the glacier moves downhill it 'plucks' the rocks frozen into the glacier from the ground.