Help on some SCs

[magnolia]

After more than four decades of research and development, a new type of jet engine is
being tested that could eventually propel aircraft anywhere in the world within two hours
or help boost cargoes into space at significantly lower costs than current methods permit.

A. tested that could eventually propel aircraft anywhere in the world within two
hours or help

B. tested that could eventually have the capability of propelling aircraft anywhere in
the world within two hours or to help

C. tested, eventually able to propel aircraft anywhere in the world within two hours,
or helping

D. tested, and it eventually could propel aircraft anywhere in the world within two
hours or helping

E. tested, and it could eventually have the capability to propel aircraft anywhere in
the world within two hours or help

[spoiler]
OA is E, my choice was A. Wonder why E is correct even though it is wordy.[/spoiler]

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For protection from the summer sun, the Mojave lived in open-sided, flat-topped dwellings known as shades, each a roof of poles and arrowweed supported by posts set ina rectangle.

A. each a roof of poles and arrowweed
B. each a roof of poles and arrowweed that are being
C. with each being a roof of poles and arrowweed
D. with roofs of poles and arrowweed to be
E. with roofs of poles and arrowweed that are

OA is A my choice was E. Thought A would mean dwellings, each a roof...

______________________________________________________________

Unlike mainstream American businesses, more than half of which fail, the failure rate for businesses in the Amish community hovers around 5 percent.
A. Unlike mainstream American businesses, more than half of which fail
B. Unlike mainstream American businesses, in which the failure rate is more than
half
C. Unlike mainstream American businesses, where more than half of them fail
D. While the rate of mainstream American businesses failing is more than half
E. While more than half of mainstream American businesses fail

[spoiler]OA is E. Could not choose the right one b/w D and E[/spoiler]

[magnolia]

This one, I believe, is from OG10:

The period when the great painted caves at Lascaux and Altamira were occupied by Upper Paleolithic
people has been established by carbon-14 dating, but what is much more difficult to determine are the
reason for their decoration, the use to which primitive people put the caves, and the meaning of the
magnificently depicted animals.
(A) has been established by carbon-14 dating, but what is much more difficult to determine are
(B) has been established by carbon-14 dating, but what is much more difficult to determine is
(C) have been established by carbon-14 dating, but what is much more difficult to determine is
(D) have been established by carbon-14 dating, but what is much more difficult to determine are
(E) are established by carbon-14 dating, but that which is much more difficult to determine is

[spoiler]OA is B. My choice was A. I assumed that we have to use "are" for a plural compound noun : determine are a, b, and c[/spoiler]

[punitkaur]

After more than four decades of research and development, a new type of jet engine is
being tested that could eventually propel aircraft anywhere in the world within two hours
or help boost cargoes into space at significantly lower costs than current methods permit.

A. tested that could eventually propel aircraft anywhere in the world within two
hours or help

Incorrect- the modifier "that" is far away from the noun jet engine it refers to. This choice conveys that the testing of the jet engine will eventually propel aircraft.


B. tested that could eventually have the capability of propelling aircraft anywhere in
the world within two hours or to help

same problem as A


E. tested, and it could eventually have the capability to propel aircraft anywhere in
the world within two hours or help

this one even though wordier than original corrects the modifier problem