Answer :
The option that will not increase the demand for bicycles in Gauteng is:
A fall in the price of bicycles.
Here's why:
1. A boycott of Gauteng by taxi operators would likely increase the demand for bicycles as people may seek alternative modes of transportation.
2. A regulation banning motorized vehicles from the city centre would also likely increase the demand for bicycles as people would need alternative means of getting around.
3. A substantial rise in the price of motorcycles and cars could lead people to consider bicycles as a more cost-effective mode of transportation, increasing the demand for bicycles.
4. However, a fall in the price of bicycles would not directly increase the demand for bicycles in Gauteng as it might not necessarily incentivize more people to purchase them compared to the other scenarios.
Therefore, among the options provided, a fall in the price of bicycles would not increase the demand for bicycles in Gauteng.