In portuguese, loja ''means'' the noun ''store''. The verb ''armazenar'' means the verb '' to store''.

loja is a noun - store,shop. ex- eu vou para loja agora (I'm going to store now) armazenar is a verb- to store. ex -As formigas armazenam comidas (the ants store foods)

Both letters work for the word 'store', as it means the same as a shop ( a place where you go to buy things you want) , for example in this sentence: ' I'm going to the bookstore in order to buy ''The Golden Compass''. (the noun 'book' comes along with the word 'store' so as to form a single word - livraria( a store that sells books) You can even say: ''That store ended up with a large stock of out-of-style clothes and just had to sell them all off''. and it can also mean to keep sth; stock or put aside(for a rainy day), for example: ' From now on I'll be storing away cash that will come in useful later on' or ' I've been storing up all these old books for a long time' hope you understood it!

The correct word is a) loja. "Armazenar" is a verb. There is also the word "amazém", that means a place where you put products to sell them after. "Armazém" is also used to define the smaller markets where you can buy many things like fruits, bread, juice and food in general. I hope that this definitions can help.