Public and private analysts are alike in their forecast of a huge rise

I shall choose E.
E removes several errors comprising of modifier issues, idioms, and meaning.

The sentence implies that Public and private Analysts are similar in that they both predict that there will be huge rise in costs of the Social Security Program in next several decades.
In A, "huge rise FOR costs" is wrong. It must be "huge rise IN costs". The awkward construction of the sentence also means that the Social Security program is spread over the next several decades.
In B, "decades of costs of the social security program" is illogical.
In C, "social security program AMONG several decades" implies that "social security program" is a quantity among "several decades".
In D, Public and private analysts OVER THE NEXT SEVERAL DECADES is wrong.
+1 E.

Hope That helps.

P.S. Modifiers should be as close as possible to the words they modify.