B, main subject should be "page seven" and it's page seven's sentences that are more understandable, so "those" is needed in B

even i marked B, but as per Kaplan its E.

1. In addition to containing more sentences than page six does, the sentences on page seven are more understandable than those on page six, with better words and grammar.
(A) the sentences on page seven are more understandable
(B) page seven has sentences that are more understandable than those on
(C) the sentences on page seven are more understandable than they are in
(D) sentences are more understandable than they are on
(E) page seven has sentences more understandable than

<In addition to containing more sentences than page six does> is a modifier. Then, what does it modify? The modifying clause modifies <page seven>. Therefore, A,C,and D are out.
Between B and E, B cannot be the answer because it doesn't agree with parallelism. <those on> does not have antecedent. E , however, is concise and right on the point. Make it as simple as possible.
<Page 7 has ...more ...than...page 6.>

2. This question reminds me of OG question regarding <seatbelt>. The gist of this argument is that bikers have the right not to wear helmets(it seems they are good at not huring themselves) and the regulations should be applied to a third party. How do we weaken? What if those bikers hurt the entire park-goers? such as increased admission $$$? That's what B says. Because bikers think that they won't cause problems but in overall, it cause a problem by raising admission fees to the park to cover the legal expenses associated with personal injury lawsuits.

I hope it helps.