Choose the correct sequence of campaigning on the western front in the European theater of operations:
a. I. Cross-channel invasion; II. Invasion of Italy; III. North Africa campaign; IV. Invasion of Sicily.
b. I. North Africa campaign; II. Invasion of Sicily; III. Invasion of Italy; IV. Cross-channel invasion.
c. I. Invasion of Italy; II. Cross-channel invasion; III. Invasion of Sicily; IV. North Africa campaign.
d. I. Invasion of Sicily; II. North Africa campaign; III. Cross-channel invasion; IV. Invasion of Italy.