Therefore, certain regions may be grouped together due to the contriant on the number of clusters（簇）, resulting in the formation of vague clusters. Further studies are required to investigate tissue heterogeneity（组织异质性）in cluster analysis. 
The above sentence is taken from the Discussion section of a published paper. Choose the correct information component(s) from the following choices.
A、Reference to previous sections
B、Review of important results
C、Comparison with existing research
D、Explanation for results 
E、Contribution
F、Applications
G、Limitations
H、Future work