OE:
The Meaning of this sentence is that policy makers are concerned about inflation, even though there are no signs that current trends in energy prices have yet caused any actual inflation. To convey this message effectively, the sentence should describe signs with a Modifier that refers to the act of driving up costs, and other descriptive elements (such as so far or an equivalent expression) should be placed in a location where it is clear what they are modifying. Finally, the sentence must explicitly express the contrast between the policy makers' concerns and the stated lack of signs in the current economy.
(A) Of increasing energy prices driving is not a correct construction; a prepositional phrase cannot have a noun + verb-ing construction as its object. To express this kind of reference, in which the entire following idea is the intended description of signs, a clause should be used. (Interpreted in a grammatically proper way, this sentence suggests that signs of higher energy prices are the things that could potentially drive up the cost of goods.) In addition, the placement of so far creates ambiguity; it could mean that there are, thus far, few signs (the intended meaning), but it could also mean that the energy prices are driving up the cost of other goods by a great deal (driving them up so far).
(B) The combination of still and remain is redundant; only one of these words is necessary. The combination of as yet and currently is also redundant. Additionally, by connecting the two clauses with a semicolon, the sentence fails to indicate the contrast between the policy makers' concerns and the lack of actual signs to warrant those concerns. Finally, inflation is a single prospect, so the plural prospects is inappropriate.
(C) In this sentence, the subject of are driving up the cost… is signs [of higher energy prices], Illogically suggesting that indicators of high energy prices, rather than high energy prices themselves, can drive up the cost of other goods. The use of both as yet and so far is redundant; only one of these construction should be used. Finally, prospect for is unidiomatic; the correct idiom is prospect of.
(D) The combination of still and remain is redundant; only one of these words is necessary. The substitution of inflation for prospect of inflation creates an unacceptable change in meaning; this choice suggests that inflation is actually happening in the economy, rather than the originally intended meaning (experts are concerned that it could happen). Finally, the present tense drive up is illogical. That tense suggests a general, permanently true fact about the economy; in other words, this wording means that there isn't much evidence that increasing energy prices drive up the cost of goods in general. The intended meaning is that the cost of goods is not being driven up at the current moment, so the present progressive are driving should be used instead.
(E) CORRECT. This choice uses a concise, non-redundant construction (remain concerned) to express the analysts' state of mind. The sentence uses despite to express the contrast between that concern and the lack of explicit signs to warrant it. Finally, thus far is placed in a location where its meaning is clear (there are few signs thus far) and the clause that … prices are driving… is properly used to describe signs.