Answer:
C). Concealed
Step-by-step explanation:
The correct word to fill the given blank would be 'concealed' as the increased growth of the 'forest of oaks, madronos, and gigantic spruces' made it almost impossible to view the abandoned building. Holker was able to see its structure, architecture, and condition only when he 'turned into the woods.' This implies that the growth of the forest concealed the building so well that it became difficult for the people to have a view of it from outside without going into the forest. Thus, option C is the correct answer.