Which of the following is a key reason why international collaborations can be challenging?
a. the collaborators may have different disciplinary and cultural backgrounds and practices.
b. there are currently no international ethical guidelines for research.
c. federal agencies are not permitted to encourage international collaborations.
d. international collaboration is rare and is on the decline.

This option could be the key reason why international collaboration can be challenging such as:

D) International collaboration is rare and is on the decline.

Explanation:

the invasive species was introduced due to commercial purpouses, as there was a demand for fur clothes and hence, a business opportunity connected to this product. actually, it was when the nutrias scaped, causing harm to the us ecosystems when they acquired the status of invasive species. in this case they have caused an environmental problem, but it could have affected also economic interests or even human health.