Questions

To change a adjective type sentence to a question, just add か (ka) at the end.

It’s new. あたらしい です (Atarashii desu).

Is it new? あたらしい です か? (Atarashii desu ka?)

For casual language, だ (da) replaces です (desu):

あたらしい だ Atarashii da.

But to change it to a question, you don’t change it to da ka.  Instead, ka replaces da.

あたらしい か? (Atarashii ka?)

Women more often drop the ka:

あたらしい? (Atarashii?)

since apparently the ka sounds abrupt when speaking casually.