These are regarded as major causes of biodiversity loss:

A. Over exploitation

B. Co-extinction

C. Mutation

D. Habitat loss and fragmentation

E. Migration

Choose the correct option:

The correct option is A, B and D only.

To understand why these options are regarded as major causes of biodiversity loss, we can analyze each of the given factors:
1. A. Over-exploitation: When humans overharvest or overexploit natural resources (such as overfishing or excessive hunting), species populations decline rapidly, leading to endangerment or extinction.
2. B. Co-extinction: When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct. For example, when a host fish species becomes extinct, its unique assemblage of parasites also meets the same fate.
3. C. Mutation: Mutation is a random change in the DNA sequence. While it is a source of genetic variation and driver of evolution, it is not considered a primary, major cause of global biodiversity loss.
4. D. Habitat loss and fragmentation: This is the most important cause driving animals and plants to extinction. Dividing vast habitats into smaller fragments due to human activities (like building roads, urbanization, or agriculture) severely disrupts species survival, especially for mammals and birds requiring large territories.
5. E. Migration: Migration is the seasonal movement of animals from one region to another. It is a natural survival strategy and adaptational behavior, not a cause of biodiversity loss.

Therefore, among the choices, A, B, and D are part of the "Evil Quartet" (the four major causes of biodiversity loss), making A, B and D only the correct choice.