A customs union is different from a free-trade area, in that:

a) a free-trade area allows for free movement of factors, whereas a customs union does not.

b)a free-trade area allows for uniform tariffs, whereas a customs union does not

c) a free-trade area removes trade barriers between member countries, whereas a customs union adopts identical tariffs with the rest of the world.

d) a customs union removes trade barriers between member countries, whereas a free-trade area adopts identical tariffs with the rest of the world.