prep1-131

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

答案没有问题，想知道D的错误，除了and so 没有  so that好。

it指代什么？

对prep的解释有点质疑

and与so都是连词，重复

prep1-95里就出现过了and so是正确答案

Unlike frogs that metamorphose from tadpoles
            into
            adults
            within
            a
            one-year period, mountain
            yellow-legged
            frogs
            of
            the
            Sierra
            Nevada
            take
            three
            to
            four
            years
            to
            reach
            adulthood, and so they are restricted
            to
            deeper bodies
            of
            water
            that
            do
            not
            dry
            up
            in
            summer
            or
            freeze
            solid
            in
            winter.

另外, 除了allows sb to do sth 较
            allow that 简洁外

想请教and so和so that的区别在哪?

不都可以表因果关西吗?

【书】承认[allow+that]

He allowed that they were right.  他承认他们是对的。

同意

【书】承认[allow+that]
                    

He allowed that they were right.  他承认他们是对的

同问，为什么so that前要有逗号？