The United Nations’ Human Development Index takes into account life ex

Major concepts
• "Take into account": idiom structure
• The use of "as well as" occasionally is correct, as is the case in this question.

• "Take into account" is an idiomatic phrase that means
"to consider carefully when you are making a decision" or
"to allow for when planning"

Idiomatic constructions either
(1) keep all three words together, this way:
To coordinate flights effectively, airlines must take into account cyclical weather such as tornadoes, hurricanes, and monsoons.
or
(2) insert a subject, X, this way: take X "into account" (to take something/someone into account):
If we take weather into account when we estimate schedules, we will manage passengers' expectations.

• AND and AS WELL AS in the same sentence

--We are allowed to use AND and AS WELL AS in the same sentence that contains a list of more than two items.
Many writers and editors do not use the construction, but that choice is one of style.
The construction is equivalent to saying "X and Y on the one hand, as well as Z on the other hand..."

Whatever comes before the phrase "as well as" typically is more important than whatever follows "as well as," but I have never seen a GMAT question force a test-taker to decide whether what follows as well as is less important. I mention the guideline to help with conceptual clarity.

-- We may use "as well as" to connect two different rhetorical or syntactic "ranks."

A balanced diet consists of fruits, vegetables, protein, and whole grains, as well as small amounts of healthy fats.

On one hand, then, a balanced diet
• consists of four very important elements: fruits, vegetables, protein, and whole grains (these four things are the greater part of the diet), and
• to a lesser extent, on the other hand, a balanced diet consists of small amounts of healthy fats

"As well as" usually signals that whatever comes after it is a less important member of the list.

Split #1: In a list of more than two items, the correct construction is
• P, Q, and R

• P and Q, as well as R
or

• P, Q, and R, as well as S

Option A incorrectly states: P, Q, as well as R
Correct: P and Q, as well as R

Just as is the case in Option A,
Option B needs to say P and Q before "as well as"

Option D adds an extra (comma + and) to the second item in the list.
Incorrect.

Eliminate options A, B, and D

Split #2: "Take into account"

Option E uses "in its account"
The idiom is strict. It should be "take into account."

Eliminate E

By POE, option (C) is correct.

Check:
The United Nations’ Human Development Index takes into account life expectancy and education, as well as income per person.
X and Y, as well as Z
That works.
In this problem, because we can eliminate options on other grounds,
we do not need to know whether "income per person" is less important than the other two items in the list.

Takeaway: do not dismiss "as well as" for lists.
(And while we are talking about urban myths, do not automatically discard "and also," either. )

Answer C