Unlike other primates, which are born with fully formed craniums, a newborn human baby’s cranium consists of eight bones that take years to fuse together fully, allowing the brain to grow much larger during those early years.
The options prompts to make quick choices among different entities. So it's a must to understand what entities are really compared.
Meaning
The primates which are born with craniums is compared eith humans which see born with different premature craniums.
The comparing entities are primates and human
A. fully formed craniums, a
newborn human baby’s craniumPrimates are compared with newborn human baby's cranium
B. fully formed craniums,
newborn human babies have craniums that
Primates are compared with newborn human babies. Logicallly only a baby can be compared with another baby, but here all primates are compared with new born human babies. So it changes the intended meaning and comparing entities.
C. a fully formed craniums, a
human baby’s craniumPrimates are compared with human baby's cranium illogical
D. fully formed craniums, a human is born with a cranium that
The comparing entities are primates and human. Logical and structure of the sentence is parallel.
E. a fully formed cranium,
the cranium pof a newborn human baby
All primates are compared with craniums. Illogical
Option D