I would say cars because just go into a city and just look around thats all you will see
Bicycles give you more gas mileage.
Depends on where you're at. In Europe and North America - certainly. Some parts of Asia probably have more bicycles and scooters than cars though.
The more people use bicycles then the fewer drive cars. This will reduce fossil fuel consumption.
NO
The country of China, even though many are switching to cars.
Bicycles are a lot more efficient than cars. On a bike 95-98% of the added energy is directly translated into forward motion, while a car would be lucky to reach 40%. While cars are definitely a faster way of transportation compared to bicycles, bicycles would probably be more efficient. Cars are very expensive and you must pay for gas. You also have to account for the distance and if its necessary to have a car for where you need to travel.
Cars and bicycles.
bicycles and cars
More bicycles
you can drive less and you can ride your bicycles and do more walking. Drive smart cars and make sure the cars are leaking less gas.
200 bicycles
bicycles, because there are more of them by far.