help with modifier problem??

[ashish1354]

As the housing affordability gap widens, middle-income families are especially hard-hit, and these families can no longer qualify to buy homes, and rising rental rates force them to use far more than the standard 25 percent of their incomes for housing, leaving them with no equity or tax write-offs to offset the expenditures.
(A) and these families can no longer qualify to buy homes, and
(B) since these families can no longer afford to buy homes, furthermore
(C) for these families can no longer afford to buy homes, yet
(D) and these families can no longer afford to buy homes; however,
(E) and these families can no longer afford to buy homes, for


Correct answer is c) but i still don,t understand the usage of for
what does it refer to ??
1)affordablity
2)familiies
3)gap

Please explain the rules for usage of , before and
sugest why is ,and wrong in this case

[reachac]

"for these families can no longer afford to buy homes, yet"
'For' is not referring to anything here, for i being used to introduce a reason/situation that "these families can no longer afford to buy homes". C is also correct for using 'yet' to show the contrast element.

P.S :- did you notice that I used for to introduce a reason in my last statement!

[NSNguyen]

https://www.beatthegmat.com/sc-1000-140-t2921.html
what is wrong with D, semicolon?