Sentence Correction

The average individual's cost of going into space is estimated at a fraction of the price per economy ticket of transatlantic airplane travel by the end of the 21st century.

A) The average individual's cost of going into space is estimated at a fraction of the price per economy ticket of transatlantic airplane travel by the end of the 21st century.

B) The average individual's cost by the end of the 21st century of going into space is estimated at a fraction of the price per economy ticket of transatlantic airplane travel.

C)By the end of the 21st century, the average individual's cost of going into space is estimated at a fraction of the price per economy ticket of transatlantic airplane travel.

D)To go into space, the cost to the average individual is estimated at a fraction of the price per economy ticket of transatlantic airplane travel by the end of the 21st century.

E)It is estimated that by the end of the 21st century the cost to the average individual of going into space will be a fraction of the current price per economy ticket of transatlantic airplane travel.

How to find core in such sentence? Also please explain how to approach this question.
OA E

eitijan wrote:The average individual's cost of going into space is estimated at a fraction of the price per economy ticket of transatlantic airplane travel by the end of the 21st century.

A) The average individual's cost of going into space is estimated at a fraction of the price per economy ticket of transatlantic airplane travel by the end of the 21st century.

B) The average individual's cost by the end of the 21st century of going into space is estimated at a fraction of the price per economy ticket of transatlantic airplane travel.

C)By the end of the 21st century, the average individual's cost of going into space is estimated at a fraction of the price per economy ticket of transatlantic airplane travel.

D)To go into space, the cost to the average individual is estimated at a fraction of the price per economy ticket of transatlantic airplane travel by the end of the 21st century.

E)It is estimated that by the end of the 21st century the cost to the average individual of going into space will be a fraction of the current price per economy ticket of transatlantic airplane travel.

How to find core in such sentence? Also please explain how to approach this question.
OA E

Hi,
generally Qs completely underlined are of higher difficulty level..
However here if you know following you can easily home on to the Correct answer

1) Estimated at-- The usage of estimated at is wrong here and it should be ESTIMATED TO BE or ESTIMATED THAT..
all except E can be eliminated

2) Average individual's cost of going..
the construction is not correct ..
the cost to the average individual of going into space IS better..

3)Antecedent of IT--
some may find it incorrect BUT in the present context and available choices, it is best

E