Answer: C) habitat loss
Step-by-step explanation:
There are over 1,200 birds threatened with extinction and of this number, 86% are classified as such because they lost their habitats. That means that habitat loss is overwhelmingly the biggest challenge facing birds today.
The habitat loss is mostly as a result of human actions such as deforestation and land degradation stemming from unsustainable forestry and agricultural practices. For instance (not in excerpt), the Amazon rainforest which is home to a lot of birds is being destroyed at an alarming rate and the clearing of forests in developing countries for settlement are some examples of human actions leading to habitat loss.