Which of these was a reason fort duquesne was so difficult to defend during the french and indian war? a) the supply lines were difficult to maintain. b) the ohio and allegheny rivers flooded frequently. c) the fort's out perimeter fencing was built with weak materials. d) the fort was built on swampy lowlands and surrounded by highlands.

The correct answer is D. The Fort was built on swampy lowlands and surrounded by highlands.

Explanation:

The Fort Duquesne seemed to be strong but manage the confluence of three rivers was a difficult task. The Fort had highlands across the Monongahela River and this situation would allow the enemy to attack it easily.

Pécaudy de Contrecœur had the intention to leave the fort in the Braddock's advance in 1755 but he could retain it because of the British's force advance. The Forbes expedition arrived in 1758 and the French had success in the Battle of Fort Duquesne which was against the English vanguard, but they had to leave the fort because of the superiority of Forbes' main force.  

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explanation:

d. islands off the coast of newfoundland