The Main Reason That There Are Relatively Few Invertebrates Categorized

The main reason that there are relatively few invertebrates categorized as endangered species is because

A) We consider other groups, such as mammals, to be more interesting and desirable
B) Worldwide, there are relatively few invertebrates when compared to plants
C) It is extremely difficult to identify and count invertebrates
D) Since there are 532 invertebrates considered endangered, none of these is true
E) Invertebrates are more numerous and the relative percentages are similar