The sentence as written contains a modification error. The modifying phrase "in attributing smoking to tobacco companies" is intended to modify "attorneys." It is the attorneys who are attributing smoking to tobacco companies. But the placement of the phrase makes it modify what comes after it—"the smokers." Eliminate (A).
A quick scan of the choices reveals a 3-2 split, with (A), (B), and (C) using the same "in attributing ...," which incorrectly modifies "the smokers," while (D) and (E) change the phrase to "if ... attributed."
(A), (B), and (C) can be eliminated right away, since they contain the modification error noted above. Compare (D) and (E).
Between (D) and (E), (D) is more concise and direct. If X is attributed to Y is sufficient, there is no need to use the wordier and more roundabout Y is attributed as the cause of X. Therefore, (D) is correct.
TAKEAWAY: A modifying phrase at the beginning of a sentence or independent clause modifies the noun that comes right after the comma. Make sure that this noun is really what the sentence intends to modify.