In terms of community ecology, why are pathogens more virulent ...

[penza]

In terms of community ecology, why are pathogens more virulent now than ever before?
A) More new pathogens have recently evolved.
B) Host organisms have become more susceptible because of weakened immune systems.
C) Human activities are transporting pathogens globally at an unprecedented rate.
D) Medicines for treating pathogenic disease are in short supply.
E) Sequencing of genes in pathogenic organisms is particularly difficult.

[plus1]

I recall doing this last year, it's C, bye bye!

[penza]

Thanks for assisting, your answer was right!