"although a preliminary hazard-zone map for ruiz, completed one month before the November 1985 eruption, clearly delineated Armero as being especially vulnerable to mudflows, emergency-response measures taken during the eruption were entirely inadequate to save the more than 23,000 lives lost when the mudflows struck."
What is the BEST meaning of vulnerable as it is used in the sentence
A) weak
B) open to
C) exposed
D) in danger of