What is the current situation of dengue?

I- The transmission of dengue has increased predominantly in urban areas and has become a major public health problem.
II- More than half of the world's population is at risk of contracting dengue.
III- The number of dengue cases has decreased in the last two decades.
IV- The number of reported cases of dengue has increased 8 times in the last two decades.
V- The transmission of dengue occurs only in tropical climate regions.
a) I, II, and IV are correct.
b) II, IV, and V are correct.
c) I, II, and V are correct.
d) Only III is incorrect.