State two ways how the event organisers were able to solve the problems regarding : (
a. zika virus (
b. waste management (
c. transport for athletes

I think that the event organizers mentioned here are the organizers of Rio Olympics. The 2016 Olympics was held in Brazil. The organizers told athletes and visitors to smother themselves with mosquito repellent to minimize the probability of being bitten and infected. They also monitored possible breeding grounds found in the Olympic sites. 

I didn't find the exact way the Rio Olympics managed their waste but this was given as an overview of how they would manage waste before, during, and after the olympics.
Waste generation avoidance → minimising volume of waste → managing inevitable waste → promoting behavioural change.

The Rio Olympics had a special card made for participants that will help them in their transit throughout the event duration. The Olympic fare card can be used on the Metro, BRTs and trains, and buses. They also partnered with two different apps to help athletes and  spectators arrive in the venue on time. 

Ithink it's a. but i could be wrong because it might be b. but it's not the other two