By steadfastly facing up to an army as indomitable as the German,
and maintaining cordial relations with as differing regimes as the US and the Soviet throughout the course of the war, and lifting the morale of a war-torn country through his inspirational speeches, Churchill not only steered Britain from definite doom but also changed the course of History
First and foremost, I looked for the obvious mistake vertically.
(D) by maintaining cordial relations with as differing regimes as the US and the Soviet through the course of the war, and by lifting the morale of a war-torn country through his inspirational speeches, not only
Churchill steered Should be "not only
did Churchill steer" to attach to the previous things Churchill did.
A is incorrect because the structure is really just exhaustive. "By FACING UP, AND X, AND Y, CHURCHILL Z" It should be "By FACING UP, X, and Y, Churchill" to logically communicate that three things were accomplished in relation to the action - CHURCHILL did X, Y and Z, to steer Britain from Doom, but he didn't do "X, AND y, AND z". the "AND" treats Y and Z almost as separate lists or non-related items.
(B)
and by maintaining cordial relations with as differing regimes as the US and the Soviet throughout the course of the war,
and by lifting the morale of a war-worn country through his inspirational speeches, Churchill not only steered
B is incorrect for similar reasons.
(C) maintaining cordial relations with as differing regimes as the US and the Soviet throughout the course of the war, and lifting the morale of a war-torn country through his inspirational speeches,
Churchill not only steered(E) maintaining cordial relations with as differing regimes as the US and the Soviet throughout the course of the war, and lifting the morale of a war-torn country through his inspirational speeches,
Churchill steered not onlyThe only difference between C and E is the
Churchill...
E is incorrect because the "steered" logically applies to "changed the course of history" and this doesn't make sense.
We should say that With X,Y, and Z, Churchill did two things: Steered and Changed.