I need some guidance for this question

Greg Mat+ Questions/Issues
1

Experts have differed about where the genus Varanus (monitor lizards) originated. Because most existing species live in Australia, early researchers concluded that Varanus originated in Australia and subsequently island hopped westward along the Indo-Australian archipelago. Herpetologist Robert Mertens later argued that Varanus probably originated in the archipelago. Chromosomal analysis has since supported Mertens’ contention, and in addition, geologic evidence points to a collision between the archipelago and the Australian landmass after Varanus evolved—a fact that could account for the genus’ present distribution.

A related puzzle for scientists is the present distribution of Varanus’ largest surviving species, the Komodo dragon. These carnivores live only on four small islands in the archipelago where, scientists note, the prey base is too small to support mammalian carnivores. But the Komodo dragon has recently been shown to manage body temperature much more efficiently than do mammalian carnivores, enabling it to survive on about a tenth of the food energy required by a mammalian carnivore of comparable size.

It can be inferred from the passage that the geographical distribution of the Komodo dragon is

A) currently less restricted than it was at the time researchers first began investigating the origins of the genus Varanus
B) currently more restricted than it was at the time researchers first began investigating the origins of the genus Varanus
C) less restricted than is the distribution of the genus Varanus as a whole
D) more restricted than is the distribution of the genus Varanus as a whole
E) viewed as evidence in favor of the hypothesis that the genus Varanus originated in the Indo-Australian archipelago

I have narrowed down my answers to either choice D or choice B, but I ended up choosing B which is incorrect. My reasoning for choice B is that Komodo dragon is more restricted because they are found “only in 4 small islands” compared to when researchers begin taking a look at the genus or the predecessor of Komodo Dragon which can only be found in Australia and migrating to the archipelago. The book chose D as the answer, but I still do not understand the book’s explanation.

I have another question about this passage and the answer choice
2

‘‘Genus = predecessor of Komodo dragon’’.is a wrong assumption.

More specifically, a genus is a taxonomic group, not an ancestor of a species belonging to it.

Option b compares the Komodo dragon’s distribution now with its distribution when researchers first began investigating Varanus.

But where does the passage tell us what the Komodo dragon’s distribution was at that earlier time? Not the distribution of the genus, but that of the Komodo specifically?

The passage discusses hypothesized past migration of the genus Varanus, not the Komodo dragon specifically. We cannot assume that what was proposed about the genus also happened to the Komodo species.

Option d, however, compares their present distributions, which the passage explicitly gives us: Varanus species are found in Australia, whereas Komodo dragons are confined to four small islands in the archipelago.

Imagine the geographical range of Komodo dragons =x and additional locations occupied by other Varanus species =y

Qa=x

Qb=x+y

Option D says Qa is less than Qb which is true.