To determine which domain is thought to be the first according to a cladogram, one would typically look for the most basal branch, which indicates the earliest divergence in the evolutionary tree.
In general, if a cladogram shows Bacteria as a separate and more basal group compared to Archaea and Eukarya, Bacteria would be considered the first domain to diverge. Conversely, if Archaea is represented as the more basal group, it would suggest that Archaea is the first. If Eukarya is depicted as branching off last, it indicates that Eukarya came after both Archaea and Bacteria.
Without the actual cladogram to refer to, I cannot definitively answer. However, based on current scientific consensus, many researchers consider Bacteria to be one of the earliest forms of life, sometimes regarded as the first domain.
Thus, if the cladogram supports that, the answer would be:
b) Bacteria
If the information was not clear or if multiple branches diverged from a common ancestor without a clear first, the answer could vary. So, if the cladogram is ambiguous, then:
d) Not enough information to tell
It's best to refer to the actual cladogram for a more definitive answer.