Among 'The Evil Quartet',which one is considered the most important cause driving extinction of species?

Of the four major causes for the loss of biodiversity (Alien species invasion,habitat loss and fragmentation,over-exploitation,and co-extinctions),which according to you is the major cause for the loss of biodiversity? Give reasons in support.

When a species becomes extinct,the plant and animal species associated with it in an obligatory way also become extinct. This phenomenon is known as:

Extinction of more than $200$ species of cichlid fish in Lake Victoria was due to the introduction of:

Among the following plants,which one would you consider an endangered plant due to over-exploitation?

Why do alien species often become invasive when introduced into a new habitat?