(a) Who is that person?
Ano hito wa dare desu ka.
(b) What is that?
Are wa nan desu ka.
In Japanese, the interrogatives dare ("who") and nan or nani ("what") are placed after the topic (marked by the particle wa), which forms who- and what- questions.
Nihon no shushō wa dare desu ka.
Who is the Prime Minister of Japan？
Kono kurasu no ukemochi wa dare desu ka.
Who is in charge of this class？
Ano tō wa nan desu ka.
What is that tower over there？
Kono hako wa nan desu ka.
What are those boxes？
That covers "what" and "who" within Japanese sentences, next to be covered will be, "de wa nai," and "de wa arimasen" hope to see you there!
°˖ ✧◝(○ ヮ ○)◜✧˖ ° こゆうきあいはら °˖ ✧◝(○ ヮ ○)◜✧˖ °