GMAT Sets answers accurate?

[vk.neni]

Hi,
I was wondering if anyone has looked into this - the accuracy of the answers provided for the GMAT Sets. I took them to be correct so far - even though sometimes I was suspicious! But the following one, where the listed answer looks clearly wrong, got me thinking.

This is a question from Set26-Verbal.

Q5)
The particular design of muscles and bones in the neck and limbs of the turtle allow that it can draw in its exposed parts such that an attacker can find nothing but hard shell to bite.
A. allow that it can draw in its exposed parts such that
B. allow it to draw in its exposed parts, and so
C. allows for it to draw in its exposed parts and that
D. allows that it can draw in its exposed parts, and so
E. allows it to draw in its exposed parts, so that

I thought the correct answer was E. The listed answer is D.

Would anyone comment on this? If the answers provided are not reliable, are there any alternative answer keys available?

Thanks a lot
vk.neni

[f2001290]

I am surprised with the OA. I will go with E