Answer:
I have found the choices that are written with this question. For ease of understanding and a better way for explaining the answer I have listed them below:
a. difficulty in classifying species
b. difficulty in classifying asexual species
c. difficulty in classifying hybridizing species
d. difficulty in classifying fossil species
e. difficulty determining when one species changed into another
Step-by-step explanation:
The evidence already exists that are required to answer these scientific questions. At this point in time scientists can use genetic data to understand the relationship between species. In some instances the data that is acquired is not enough or it is damaged and not well preserved. Here, along with palaeontologist the scientists can use all the evidence they find to better create cladograms and classification charts to date back our common ancestors.
Even with this great scientific tool it is still a challenge to properly identify the speciation to H. sapiens. The continued advancements in science is closing the gap on these set backs and hopefully in time this can be overcome.
In conclusion, the answer here is d. It is currently a challenge identifying fossil species.