The Federal Reserve bond buyback program has buoyed Wall Street,
and helped the stock market reach record highs, but yet to translate into consistent job growth across the country. a. and helped the stock market reach record highs, but [auxiliary verb] yet to translate into consistent job growth across the country
Wrong. Need auxiliary verb. If we say "but yet", we cannot determine the tense.
b. helped the stock market reach record highs, but it has yet to translate into consistent job growth across the country
Wrong. Need "and" before "help the stock market". The correct syntax is "X and Y, but Z" in which X and Y are parallel.
c. helped the stock market reach record highs, and has not translated into consistent job growth across the country
Wrong. Same as B. We need "and".
d. and helped the stock market reach record highs, but it has yet to translate into consistent job growth across the country
Correct. - The usage of "and" is correct.
- "has yet to translate" is correct grammar (even though it is used quite rarely). This syntax has negative meaning.
- "It" clearly refers to "the Fed program"
e. and helped the stock market reach record highs, but has not translated into consistent job growth across the country
Wrong. E has pronoun problem.
E says: The Fed program has buoyed X, and helped Y reach record highs, but has not translated into Z.....
What has not been translated? The Fed Program or Y (the stock market). E may convey a different meaning: the Fed Program helped the stock market reach record highs, but has not translated
the stock market into consistent job growth.... Thus, the meaning is quite ambiguous.
We need "it" to refer "the Fed program".
Hope it helps.