Option A: “fly” means to maneuver through the air as a bird does with its wings or as an aircraft does. This is not the correct meaning of the underlined word. Thus, option ‘A' is wrong.
Option B: “dismantle” means to disconnect the pieces. This is not the correct meaning of the underlined word. Thus, option ‘B’ is inaccurate.
Option C: “support” means to offer assistance or bear the support of something. This is not the correct meaning of the underlined word. Thus, the choice ‘C’ is inaccurate.
Option D: “increase” means to travel up or become greater in number, intensity, size, or quantity. This can be identical to “mount”. Within the given sentence the word mount refers to a rise in number. 

Hence, option D is the correct answer.