Sentence Correction

dear friends,
please help, HELP, HELP

To develop more accurate population forecasts, demographers have to know a great deal more than now about the social and economic determinants of fertility.
(A) have to know a great deal more than now about the social and economic
(B) have to know a great deal more than they do now about the social and economical
(C) would have to know a great deal more than they do now about the social and economical
(D) would have to know a great deal more than they do now about the social and economic
(E) would have to know a great deal more than now about the social and economic

I am confused about comparison omit in E,
IMO, the two comparisons' subject are same (demographers) and verb (have), so subject and verb can be omit, but OA says, falsely compare between what demographers need to know and now.

another question, omit same verb.
According to recent studies comparing the nutritional value of meat from wild animals and meat from domesticated animals, wild animals have less total fat than do livestock fed on grain and more of a kind of fat they think is good for cardiac health.
(A) wild animals have less total fat than do livestock fed on grain and more of a kind of fat they think is
(B) wild animals have less total fat than livestock fed on grain and more of a kind of fat thought to be
(C) wild animals have less total fat than that of livestock fed on grain and have more fat of a kind thought to be
(D) total fat of wild animals is less than livestock fed on grain and they have more fat of a kind thought to be
(E) total fat is less in wild animals than that of livestock fed on grain and more of their fat is of a kind they think is

Why B in 2nd question is correct, while E in 1st question is incorrect ?
I am confused now.
can any experts or instructors clarify for me.

thanks in advance

zoe wrote:dear friends,
please help, HELP, HELP

To develop more accurate population forecasts, demographers have to know a great deal more than now about the social and economic determinants of fertility.
(A) have to know a great deal more than now about the social and economic
(B) have to know a great deal more than they do now about the social and economical
(C) would have to know a great deal more than they do now about the social and economical
(D) would have to know a great deal more than they do now about the social and economic
(E) would have to know a great deal more than now about the social and economic

I am confused about comparison omit in E,
IMO, the two comparisons' subject are same (demographers) and verb (have), so subject and verb can be omit, but OA says, falsely compare between what demographers need to know and now.

You need to understand what is being compared here.
In this sentence, we are comparing knowledge.
The option E compares knowledge that "now". Clearly this is not the right comparison

zoe wrote:another question, omit same verb.
According to recent studies comparing the nutritional value of meat from wild animals and meat from domesticated animals, wild animals have less total fat than do livestock fed on grain and more of a kind of fat they think is good for cardiac health.
(A) wild animals have less total fat than do livestock fed on grain and more of a kind of fat they think is
(B) wild animals have less total fat than livestock fed on grain and more of a kind of fat thought to be
(C) wild animals have less total fat than that of livestock fed on grain and have more fat of a kind thought to be
(D) total fat of wild animals is less than livestock fed on grain and they have more fat of a kind thought to be
(E) total fat is less in wild animals than that of livestock fed on grain and more of their fat is of a kind they think is

Why B in 2nd question is correct, while E in 1st question is incorrect ?
I am confused now.
can any experts or instructors clarify for me.

thanks in advance

In this question, we need to compare the wild animals. Option B correctly compares wild animals with the livestock.
Hence the correct option.

Does this help?

OptimusPrep wrote:You need to understand what is being compared here.
In this sentence, we are comparing knowledge.
The option E compares knowledge that "now". Clearly this is not the right comparison

thanks so much for your answer.

I think I have a big problem about comparison.
To develop more accurate population forecasts, demographers would have to know a great deal more than now about the social and economic determinants of fertility.
here, IMO, demographers would have to know a great deal more than (they would have to know a great deal ) now about .....
here, E omits "they would have to know", there are two comparisons, condition that demographers would have to know a great deal and another situation that they would have to know deal now..

so I think E is correct..

please clarify my fault.

thanks a lot

have a nice day