It is well established that the death of a

great question.

E is wrong because that -clause is not prefered to be a grammatical subject. the pattern in D is prefered.

this case happen in og, but is very hard for us to apply

What does it mean---> people can be insecure as adults

People (who experience...... parent) can be as insecure as adults..

The author wants to convey that
People who lost their parent during their childhood can be as insecure as adults (who experience it)

So children are the people, the author is talking about.

I think you might be confused with the usage of "as" here.

Here are my 2 cents on the usage of "as" -

"As" can play 2 roles, majorly.

One, it Is used for comparison (similarity)
Eg. I like to drink water as much as i like to eat a chocolate.
We are comparing 2 clauses here.

It can also be used to compare nouns but "as" will need a verb, unlike "like" (if you're not aware)

As her brother did, Ava aced the test.

Or
Ava aced the test, as her brother did.

Second, "as" can be used to present a role
Eg.
He will be joining as the assistant director of the company.

Here in the sentence above, option E uses "as" as I used it in the second usage.

So parent can be "as" adults
They are parents and adults at the same time.. it causes reader to read it again to understand it. Hence, there is lack of clarity in this sentence.

Therefore, D, with its clear construction, here is better than E

Posted from my mobile device

ammuseeru

Just to add one detail to Shrey9 's reply:

"People can be insecure as adults" means that people can FEEL insecure WHEN they become adults.

Stated differently, a child who loses a parent to death can grow up to be an adult who feels insecure.

The word AS can also be a conjunction that means when, during the time that, or while.

Hope that helps.

Can any expert please help me to understand how option D is better than option E

A. It is well established that the death of a parent during childhood can cause insecurity in adults. -- "parent during childhood" is kinda illogical.

B. It is well established that the death of a parent when a child can cause insecurity in adults. -- "death.. when a child can cause" more illogical than A.

C. It is well established that the death of a parent occurring when a child can cause insecurity in adults. -- "death.. occuring when a child can cause"

A, B and C are illogical. What is established is that people who experienced trauma (death of P) in childhood can be something something as adults. The above options do not bring out this meaning and whatever they bring out is very illogical.

D. It is well established that the people who during childhood experience the death of a parent can be insecure as adults. -- Correct.

E. That people who during childhood experience the death of a parent can be insecure as adults is well established. -- Passive voice. Couldn't find any other error.