A.)
1. The larger the city is, the larger the population becomes, and the higher the crime rate can be.
2. A large city has many options for criminals to hide and blend in.
3. Traffic
B.)
1. You don't know the place, so you'll get lost.
2. If you don't know your way, some taxi driver might take advantage of that and take the long road.
3. If you go on a holiday at a foreign country with a different language, then that'll become a problem with communicating with people.